_______the past two months he has been busy with his school work.
Lucy and Lily are twins, but they are different _____each other in many ways.
It is necessary for students ______ good studying habits.
--I think people here are friendly. Do you _______me? --Yes, you are right.
Yangtze River is one of ______rivers in the world.
--Would you like some chocolate? --No, thanks. I ______ eat chocolate. It is bad for my health.