–You’ve got a stomachache? But we ate at the same place. How come my stomach is fine? --You have an iron stomach! Mine isn’t ___ strong. 

The research lacks  evidence, and therefore, its conclusions are doubtful.

Glass is _______ and must be handled with great care.

It was a really_____experience. Afterwards everybody was very_____ .

—How is your recent trip to Sichuan? —I’ve never had ______ one before.