Everyone knows that _____ sun is in the center of the solar system（太阳系）

Do you often get online?— Yes. I ______ lots of time on it. It’s a good way to kill time.

Sandy sits in front of Amy, but behind Simon. So Sandy sits ______ Amy ______ Simon. [ ]

Have you found the information is about President Xi’s visit to Russia?— Not yet. I will surf the Internet.

I saw ___ eighty-year-old man with ____ umbrella in such a sunny day just now.