You cannot understand everything clearly unless__________ (Complete the sentence with suitable clause/phrase)

Patriotism is a noble virtue. It is high time  we practiced patriotism/to become patriots

Hasan got GPA 4.50. Had he studies seriously he would have got/gotten GPA 5.00

Time is valuable. Those who waste time suffer in the long run / cannot succeed in life.

This celling is not so high. He is tall enough to touch the ceiling

Lock the door and keep the key in a safe place lest you should/might lose the key

A lot of passengers were waiting at the bus stop. A bus came. But the bus was so small that it could not take all the passengers