24.The students were ____ over the ____ problem, listening to the teacher with a ____ expression on their faces.
After several years of observation, the research group ______ the conclusion that language acquisition is faster when students ______ to the situation where it is spoken.
It will be many years ______the doctors and medical scientists can find _____ for cancer.
We have to ______ everything question in detail ______ we take action.
It is clear that no use can be made ______radium _____we don’t know clearly the characteristics of it.
From my point of view, the theory that ______ by the scientist is not quite scientific.