问题


There is a single choice question about abstract algebra. Answer the question by replying A, B, C or D.
Question: Statement 1 | A factor group of a non-Abelian group is non-Abelian. Statement 2 | If K is a normal subgroup of H and H is a normal subgroup of G, then K is a normal subgroup of G.
A. True, True
B. False, False
C. True, False
D. False, True
Answer:

答案

模型 模型答案 正确答案
金声玉亮2.0 B B
deepseekr1

The correct answer is **B. False, False**.

**Analysis:**

1. **Statement 1:** A factor group of a non-Abelian group is non-Abelian.
- **Counterexample:** The symmetric group \( S_3 \) is non-Abelian. Taking the normal subgroup \( A_3 \) (alternating group of order 3), the factor group \( S_3/A_3 \) has order 2 and is cyclic (hence Abelian). This shows a non-Abelian group can have an Abelian factor group, making Statement 1 **false**.

2. **Statement 2:** If \( K \trianglelefteq H \) and \( H \trianglelefteq G \), then \( K \trianglelefteq G \).
- **Counterexample:** Let \( G = A_4 \), \( H \) be the Klein 4-group (normal in \( A_4 \)), and \( K \) a subgroup of \( H \) of order 2 (normal in \( H \)). Conjugating \( K \) by elements of \( A_4 \) (e.g., conjugation by \( (123) \)) results in elements outside \( K \), proving \( K \not\trianglelefteq G \). Thus, Statement 2 is **false**.

Both statements are false, so the answer is **B**.
B
gpto1 B B
GPT-4o D. False, True B
llama3.1-70B-Instruct

B
B
llama3.1-405B-Instruct

A factor group of a non-Abelian group can be Abelian. For example, consider the dihedral group D4 = {e, a, a2, a3, b, ab, a2b, a3b} where a4 = e, b2 = e and ab = ba-1. The subgroup H = {e, a2} is normal in D4 and the factor group D4/H is Abelian. Therefore, statement 1 is false.

If K is a normal subgroup of H and H is a normal subgroup of G, then K is a normal subgroup of G. This is because if k is an element of K, h is an element of H, and g is an element of G, then ghk = (ghg-1)(gkg-1) is an element of K since H is normal in G and K is normal in H. Therefore, statement 2 is true.

The correct answer is D. False, True.
B
DeepSeek-Coder-V2 B. False, False B
Qwen2-72B-Instruct D. False, True B
baichuan4 D B
doubao D. False, True

Counterexample for Statement 1: The factor group of the non-Abelian group S_3 (symmetric group on 3 elements) by the normal subgroup A_3 (alternating group on 3 elements) is Abelian.

Statement 2 is a well-known result in abstract algebra and is true.
B
minimax D. False, True

Explanation:
Statement 1 is false because a factor group (also known as a quotient group) of a non-Abelian group can be Abelian. For example, consider the symmetric group S3, which is non-Abelian, and its normal subgroup A3, which is the alternating group consisting of even permutations. The factor group S3/A3 is isomorphic to Z2, which is Abelian.

Statement 2 is true because if K is a normal subgroup of H and H is a normal subgroup of G, then for any g in G and k in K, we have gkg^(-1) in H (since H is normal in G) and also in K (since K is normal in H). Therefore, gkg^(-1) is in K, which shows that K is normal in G.
B
kimi C. True, False

Statement 1 is true because a factor group (also known as a quotient group) of a non-Abelian group can be non-Abelian. The commutativity of a group is not necessarily preserved in its factor groups.

Statement 2 is false because the normality of a subgroup is not transitive. If K is a normal subgroup of H and H is a normal subgroup of G, it does not necessarily mean that K is a normal subgroup of G. Normality is a property that depends on the specific group and subgroup in question, and it is not inherited in the way that the statement suggests.
B
wenxinyiyan D B
zhipu The correct answer is B. False, False.

Explanation:

**Statement 1: A factor group of a non-Abelian group is non-Abelian.**
This statement is false. It is possible for a non-Abelian group to have an Abelian factor group. For example, consider the symmetric group \( S_3 \), which is non-Abelian. The subgroup \( A_3 \) (the alternating group of order 3) is normal in \( S_3 \), and the factor group \( S_3 / A_3 \) is isomorphic to \( \mathbb{Z}_2 \), which is Abelian.

**Statement 2: If K is a normal subgroup of H and H is a normal subgroup of G, then K is a normal subgroup of G.**
This statement is also false. The property of being a normal subgroup is not transitive. A counterexample is the dihedral group \( D_8 \) (the group of symmetries of a square). Let \( K \) be the subgroup of rotations by 90 degrees, \( H \) be the subgroup of rotations (which includes \( K \)), and \( G \) be \( D_8 \). \( K \) is normal in \( H \) and \( H \) is normal in \( G \), but \( K \) is not normal in \( G \).

Therefore, both statements are false, making the correct answer B. False, False.
B
gpto1 B B
deepseekv3 The correct answer is **D. False, True**.

### Explanation:

1. **Statement 1**: A factor group of a non-Abelian group is non-Abelian.
This is **False**. A factor group \( G/N \) of a non-Abelian group \( G \) can be Abelian. For example, the symmetric group \( S_3 \) is non-Abelian, but its factor group by the alternating group \( A_3 \) is Abelian (since \( S_3/A_3 \cong \mathbb{Z}/2\mathbb{Z} \), which is Abelian).

2. **Statement 2**: If \( K \) is a normal subgroup of \( H \) and \( H \) is a normal subgroup of \( G \), then \( K \) is a normal subgroup of \( G \).
This is **True**. Normality is transitive in this case: if \( K \triangleleft H \) and \( H \triangleleft G \), then \( K \triangleleft G \).

Thus, **D. False, True** is the correct answer.
B