1．She failed this English examination again. This is because she sometimes has trouble ____________(pay) attention to her study.
答案：paying
2．The problems ____________(discuss) at the meeting tomorrow are really hard____________(solve)．
答案：to be discussed；to solve
3．____________(remind) myself of the past pleasant days, I have some related photos pinned beside my desk.
答案：To remind
4．____________(wait) for the bus for thirty minutes, he lost his patience and felt very anxious.
答案：Having waited
