Someone is ringing the doorbell. Go and see _____.
A person ________ with H7N9 viruses will be more likely to die of lung dysfunction.
The children talked so loudly at dinner table that I had to struggle _________
At present, computer knowledge has become ___________ requirement as the ability to read and write.
Make sure the gas is turned off after a bath, which would ________ cause danger.
Bats are surprisingly long-lived creatures, some ________ a life span of 20 years.