I fail to pass the exam although I worked very hard. I should ______ the causes of my failure.

Many airlines offer one-service flights, especially on short, ____ traveled routes.

There are several ways in which airline service can be ____ categories.

Every airline＇s flight has a number to ____ it.

Once ____, twice shy.

Goods, such as fruits and flowers are ____.

She apologized for ____.

Quick delivery is the most obvious ____ of air freight service.

Mr.Li ____ the composition once a week last term.

For goods of high unit value, shippers usually pay extra ____.

The poem is said ____ into many languages.