The professor you referred to in the letter______ usstudents three lectures by next Monday.

Work hard, and you’ll have success of _______own. Don’t give up for _______ reason.

Stop making so much noise ____ the neighbor will start complaining

There were more than 80 passengers on board then, but only one boy named David____the airplane crash.

观察下面4个选项,从中选出不同类的选项。