a variety of exercises___(is/are)indispensable for students to master the knowlege of the subject.

a great variety of是什么意思 a variety of 和the variety of 的区别? the variety of和a variety of一样吗?为什么 the variety of,a variety of 的区别? all variety of与a variety of有区别吗 integration of a variety of resources是什么意思? “a variety of”的中文意思是? 用 a wide variety of 造句 用a variety of怎么造句 Eat a variety of nutrient-rich foods. 用a variety of怎么造句 to arrange variety of party foods 为什么不是 to arrange a variety of party foods? 英语：a variety variety 音标! a variety of与various of的区别是什么?如上～ a variety of 和varieties of的用法 a variety of与various of的区别是什么? a variety of 的用法a variety of food还是foods,a large number of 用可单还是可复 英语口语发音a wide variety of items variety of of的o音不发?variety of items 这三个应该连在一起吗?