Important _______ having an ambition is, it must be channeled in the right direction. Otherwise, it would ruin ourselves and others.

Miss Li always makes her classes lively and interesting.-Sure, I still remember every word ______ she said at school.

Like any other _____ here, he can walk ______ his two hands.

(2013·潍坊高考模拟)Air pollution is getting more and more serious，so we must take action________it is too late

b is with _______ hours: one can work in the morning or in the afternoon, so long as work for no less than five hours every day.