Boys and girls usually _____ and play tricks on each other on that day.

Future will be a marvelous world of artificial ______—–robots might have their emotions and we human beings might have robots asfriends

Timmy often gets full marks in the exams, but he nevershows off. He is very ______.

he aid from the whole country, the people in theflooded area of northeastern China managed to______thisunforgettable summer of 2013

下列各句中，加横线的成语使用正确的一项是（ ）