He tried his best to solve the problem, difficult it was.
While reading, you’d better make a mark ___ you have any questions.
Don’t keep your mouth ___ if you want to improve your spoken English.
My classmate, Li Ming, was highly praised for ___ a good deed.
Sunglasses can ___ us from strong sunlight.A. hold B. prevent C. protect D, make
There are many pine trees on ___ of the street.