通常用于检测IgM类抗体的ELISA技术类型是（）
A.双抗体夹心法
B.间接法
C.竞争法
D.捕获法
E.直接法
参考答案：D
— How far are you cycling each day?
— ____. It will depend on the weather. [ ]
A. It's my pleasure
B. It's hard to say
C. Take care
D. Good luck on your journey
已知a+b=3，且a﹣b=﹣1，则a2+b2=（ ）．
