题干
He was _____ by his grandparents, so his parents seemed to be strangers to him.
A：brought out
B：brought dow
C：brought i
D：brought u
答案(点此获取答案解析）
D
A：brought out
B：brought dow
C：brought i
D：brought u
面积的2倍，这种细胞材料最可能是 （ ）