介导体液免疫的是()
A.LAK细胞
B.T细胞
C.K细胞
D.B细胞
E.NK细胞
参考答案:D
Our English teacher is very nice. We _____ friends since three years ago. [ ]
A.were
B. became
C. have been
D. have made
冷校法是基于()原理来校正变形零件.
A.变形
B.反变形
C.热胀冷缩
D.变形强化