Scientists think they have _____ in their attempt to find the causes of some major dieases.
Margie shows a very positive attitude ____ her work.
The manager insisted that the work ____ finished by the end of this month.
My elder sister ____ me into buying the red mountain bike.
Although I often send e-mails to Tom, I have never seen him _____________.
The police asked him to _________what he had seen.