According to the passage，a great variety of influenza strains can appear when______.

Having acknowledged receipt of the interview letter，you must prepare for the interview. Firms usually take a good deal of trouble over interviews，and there may be three or more people present，which can be a little frightening. Very often the personnel officer will begin by some words of welcome and an invitation to you to tell them a little about yourself. This is really inviting you to repeat the information you have already supplied on the application form，and which they have already read，but it does have some point. It will put you at your ease，because at least you know all about your own level of achievement and can speak about it confidently. It helps them assess your ability to communicate and your serf-esteem. Some people have too high an opinion of themselves，some take an unduly pessimistic view of their achievements，while others have a nicely balanced assessment of their own abilities.

食物短缺并不像你报道的那么严重。

我们提出了抗议，但没有效果。

 如果我们早点动身，现在就不会在雨中走了。

如果你束手无策，就听其自然好了。

Between labor and play______(stand)work.

她的社交活动妨碍她的学业。

______(increase)，new technology is making it easier for us to find alternative methods of testing.

______(win)the presidency，a candidate must receive at least 270 votes. an electoral majority.

He took his umbrella with him lest it______(rain).