“Entailment” can be illustrated by the pairs ________.
选项：

A:(a) He married a blonde heiress. (b) He married a blonde.
B:(a) He has been to Europe. (b) He has been to France.
C:(a) He has a sister. (b) He is not an only child.
D:(a) He doesn’t have a sister. (b) He has a brother.