When we ran out of the house, we could see a helicopter ______.

This is one of the issues that deserve ______.

There has been an increasing number of ______ in primary schools in the past few years.

I can＇t put up with _______.

Nobody heard him sing,______?

She is a better speaker than ______ in the class.

Among the four sentences below, Sentence ______ expresses the highest degree of possibility.

How can I concentrate if you _______ continually ______ me with silly question?

You must fire ______incompetent assistant of yours.

At that moment(过去时）, with the crowd watching me, I was not afraid in the ordinary sense, as I ______if ______ alone.（虚拟语气）

Some Martian rock structures look strikingly like structures on Earth that are known _______by microbes.