参与再循环的淋巴细胞主要是（）。
A.成熟T细胞
B.成熟B细胞
C.不成熟T细胞
D.不成熟B细胞
E.记忆性B细胞
参考答案：A
What do you do the weekend?[ ]
A. on
B. at
C. in
There are _____ products to be sold in the factory store. Which of the following is NOT correct? [ ]
A. a large number of
B. plenty of
C. a large amount of
D. a great many
