Why did you laugh just now—Ted wanted to tell us _____ very funny story， but he forgot ______ ending himself.

Tom isn’t feeling very well. —He seems to have a cold the weather changes suddenly.

There are some health problems that, when _______ in time, can become bigger ones later on.

On the top of the mountain two towers built more than 500 years ago.

Those who can achieve high grades in class tend to be weak in handling some practical problems, ________ is often the case.