15. Three quarters of the land here ____

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问题选择题

15. Three quarters of the land here _____ wet land, an ideal place for migrating birds.

A．are

B．is

C．have been

D．Being

答案

解答题

已知函数f(x)＝4x³＋3tx²－6t²x＋t－1，x∈R，其

中t∈R.

①当t＝1时，求曲线y＝f(x)在点(0，f(0))处的切线方程；

②当t≠0时，求f(x)的单调区间．

选择题

The most widely accepted theory about the beginning of drama is based on the concept ______ drama evolved from ritual.

A．which

B．that

C．when

D．as