A:①②
B:③④
C:②③
D:①④
若4a2﹣(k﹣1)a+9是一个关于a的完全平方式,则k=____
有数组{1,2,3,4},{2,4,6,8},{3,6,9,12},…,那么第100个数组的四个数的和是____ .
用适当的介词填空
What do you like doing ____the evening?
Thanks ____ your letter.
Look ________ the blackboard and listen____me.
We begin classes ____ about 8:00.