Ladies and gentlemen，please return to your seat and fasten your safety belt. Our plane_________.

Remember to wash your hands __________ you have meals.

178My brother has _____ the army for more than five years

After two years’ research, we now have a ________ better understanding of the disease

ody has ______ responsibility to save water, iffuture generations are to enjoy _____ similarstandard of living to the one we enjoy now