Fact 1: All chickens are birds. Fact 2: Some chickens are hens. Fact 3: Female birds lay eggs.
If the first three statements are facts, which of the following statements must also be a fact? I. All birds lay eggs. II. Hens are birds. III. Some chickens are not hens.
I. II only
II. II and III only
III. I, II and III
IV. None of the statements is a known fact.

Question: 以下哪项是正确的？
Options:
A. III 或 I, B. 只有 II, C. 仅 I, D. I 或 III, E. 仅 IV
Answer: B
True statement: II