This factory produced much dirty water, which resulted in a wide _______ of environmental problems.
Some people are good at _____ voices on the phone while others ______.
Pandas are native ______ China.
No product is allowed to go into the market if it fails to _____ the quality standard.
When was it _____ your parents took you to Hangzhou?
It is everyone’s duty to ______ our school a pleasant place to learn in.