39. I don't know (whether to ask) the question or not.
40. He appeared well (prepared) for the TV debate.
42. (The longest) I can stay is three hours.
45. The picking of the fruit, (for which) work they receive no money, takes about a week.
47. - Have you met our German neighbours?
- Are they (the ones) who moved here recently?
其实 42 也可以填 the longest time ,但 time 通常被省略.
我是加拿大人,前英语老师.