問題詳情：
Generally, students' inner motivation with high expectations from others ________ essential to their development.
A. is B. are
C. was D. were
【回答】
A 句子的主語爲students' inner motivation爲單數概念，可排除B和D選項；根據句意可知句子講的是客觀事實情況，應用一般現在時，故*爲A項。
知識點：主謂一致
題型：選擇題
