Jean Wagner’most s enduring contribution to the study of Afro -American poetry is his insistence that it ________ in a religious, as well as worldly, frame of reference.

Our payment terms (付款方式)are ___ , irrevocable letter of credit for the full invoice value.( )

By "language acquisition is primarily the acquistion of the grammatical system of language", linguists mean that ______.

They wrote a letter of thanks to ________ had helped them.

As for family education, parents are encouraged to rely on ________ rather than punishment.

They ________ extensive and possibly dangerous actual flight training.

In the Grammar-Translation Method, grammar analysis and translation proved to be _______ in studying foreign culture through literary works.

Scientists doubt wheth er it ’s ________ to regulate one ’s biological clock by drinking.

This offer is firm, subject to your immediate reply ____ should reach us not later tha n the end of this mon th.( )

The house was quiet in the night, ________ the occasional coughing from my throat.