Question

______ takes a lot of concentration and a great sense of balance to stay on it.

A．It

B．This

C．What

D．That

Answer 1

A

试题分析：句意：这需要高度的专注和很好的平衡感才能站在上面。这里使用it做形式主语，句型是:It takes sth to do …..，it是形式主语，不定式是真正的主语，所以选A。