Question

必须采取措施来阻止他参加校篮球队的选拔。

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Answer

Something must be done to stop/ prevent/ keep him from trying out for the school basketball team.

Action must be taken to stop/ prevent/ keep him from trying out for the school basketball team.

【解析】

必须采取措施Something must be done/ Action must be taken；阻止他做某事stop/ prevent/ keep him from doing sth；参加……的选拔(角逐) try out for；校篮球队the school basketball team .本句需用不定式表目的，根据句意和语法可知，要用含有情态动词的被动语态，故答案为Something must be done to stop/ prevent/ keep him from trying out for the school basketball team./Action must be taken to stop/ prevent/ keep him from trying out for the school basketball team.