题干
When I get puzzled about some difficult problems, my teacher always encourages me and says, “Take it _________ .”
A：for granted
B：seriou
C：simple
D：easy
答案(点此获取答案解析）
D
质分子，其分子大小、电荷的性质和数量情况如右图所示，下列有关蛋白质分离的叙述正确的是