This is the third time the famous scientist __________ the United States.
Would you like to go for a picnic with us—_____, but I’m too busy.
下列各句中,划线的成语使用恰当的一项是( )
Why didn’t you try your best to get on the subway? — I tried to, but it started moving______ I could get on it.
Though great efforts have been on their study , Annie still can’t make any improvements , which makes her parents greatly ______