透射电镜中物镜的作用是（）
A、电子源
B、会聚电子束
C、形成第一副高分辨率电子显微图像
D、进一步放大物镜像
参考答案：C
—Excuse me, are these books ________?
—No, they aren’t ________. They are ________ classmate’s.
A. his; my; his B. your; mine; his C. yours; mine; my
集体抉择
