This is the bady ()he is looking after .这题答案是 whom ,定语从句题.先行词baby是人,又后面从句的宾语 who 先行词是人,又后面从句的主语 例句 He is the person who found my wallet. which 先行词是物,又后面从句的主语或者宾语 I don't like this cup of coffee which tastes too sweet.
This is the bady (whom)he is looking after 因为是baby所以是被looking after的,baby在从句中是宾语,所以用whom I don't konw whom he will go with tommorrw. This is the boy who is looking after the baby.