问题补充：
students are playing on the playground. students there is at least over 100.
A. A number of; A number of
B. The number of; The number of
C. A number of; The number of
D. The number of; A number of
答案：
A. A number of; A number of
B. The number of; The number of
(答案→)C. A number of; The number of
D. The number of; A number of
解析：本题的含义是许多学生正在操场上玩，在那儿的学生数至少超过一百人，a number of表示许多的含义，the numberof表示……数目，故本题选C。
