单项选择题A.They should help maintain the equipment.B.They should keep a watchful eye on their children.C.They should stop their children from climbing ladders.D.They should teach their children how to use the equipment.
单项选择题A.Because it was their hometown.B.Because they wanted to help the AIDS patients.C.Because they were doing their summer social topics.D.They were learning medicine and doing research on HIV.