都正确,但中心词和修饰语各不同,后面括号只写中心词,另一个就是修饰语:
1.We had to sit through nearly 2 hours of speech. (hours 为中心词)
2.We had to sit through nearly 2 hours’ speech.(speech 为中心词)
3.I will get $500 for 3 hours’ work.(work 为中心词)
4.I will get $500 for 3 hours of work.(hours 为中心词)