They were talking about the persons and things _______ they saw in the factory.
Smile to the world, ________ the world will smile back to you.
-- ________ can you finish this English examination?-- In about one and a half hours.
-- Would you like some milk?--________.
You __ drive your car so fast. It's very dangerous.
--What is Miss Gao's favourite________?--She is always in pink. Don't you know?