When a space shuttle has accomplished its _____, it can be ready for another trip in about two weeks.

When delivering a speech, you should adjust your language to the age of your ______ audience.

His latest research is at the   of genetic science. 

The members of the club wouldn't run a _____ in entrusting（委托） the organization to an unreliable person.

Peter isn’t______ at all; he always pays the bill when we eat in a restaurant.