Huang Bo is a popular film star. He          brings us good films.

Though they are______little children , they have worked out _______many difficult math problems.

—Dad, science is too hard for me.—Oh, dear, if you keep listening ________ in class and do enough exercises, you’ll find it easy.

The problem is so ______________ that I can solve it ________________.

— You must keep the door _______ when you leave your room. — But I want to get the fresh air. I think I can keep the window ________ instead.