Air and the sun's rays create much distortion, and whatever tends to _____ their influence is useful to the astronomer.

I couldn't afford to rent a house like this,______buy it.

This Englishman is good at writing, reading and ＿＿＿＿＿ is kind to others. 

It was amazing that the army _______ its homeland against all enemies.

The naughty boy who _____ in bed ____ to his parents, saying that he was ill and  couldn’t go to school.