The BBC's documentary Du Fu：China's Greatest Poet explains ________ Du's works have been popular for centuries.
A.when B.whether C.why
With the help of Air Classroom, students ________ keep learning even with schools closed.
A.can B.must C.should
Drugs are harmful to people's physical and mental health. We teenagers must ________ them.
A.take care of B.keep away from C.get used to
—Pingtang Bridge has the highest concrete bridge tower in the world.
— ________ amazing it is!
A.How B.What C.What an
As we all know, using public chopsticks ________ necessary when we eat with others.
A.is B.are C.was
After-school activities help students gain more skills and teach ________ to care about others.
A.me B.you C.them
