When it ________ air pollution, Beijing faces the three “C”s, cars, coals and construction, which lead to Beijing’s thick air pollution.
You have done so much work—you ______ pass the exam.
It's clear that neither he nor his parents______ the plan put forward at the family meeting.
She has worked at the bank for many years,nine ______.
The plane cannot ______ or land safely every time.
______ Chemistry is a branch of Chemistry.