This is _____ pen and ________ is in the pencil-case.

s the first time you _____Chengdu —–No But the first time I _____here, the citywasn’t so beautiful

Why do you look worried?— Because what I am really concerned about is _____my friend can do me a favor or not.

The market competition is fierce, but our products have great advantage ______ quality and price

The problem of global warming is serious.______，the sea levels have risen a little.