第21届世界杯足球赛开幕式于2018年6月14日在俄罗斯举行．
The opening ceremony of the 21st FIFA World Cup in Russia on June 14， 2018．
The music by Tan Dun sounds quite exciting．（改为感叹句）
the music by Tan Dun sounds！
Mary is very busy．She does not have any time for social activities．（合并为一句）
Mary is busy have any time for social activities．
He can't finish the task in time if nobody helps him．（保持句意基本不变）
He can't finish the task in time ．
Lucy exercises every day to keep fit．（对划线部分提问）
Lucy exercises every day？
We held a welcome party for the exchange students yesterday．（改为否定句）
We a welcome party for the exchange students yesterday．