There was a teapot fashioned like a china duck, out of ______ open mouth the tea was supposed to come.

单项选择题John Wagner's most enduring contribution to the study of Afro-American poetry is his insistence that it ______ in a religious, as well as worldly, frame of reference.

单项选择题The largest system serving e-mail messengers is the Internet, a ______ of millions of computers linked worldwide.