A:p=7 q=18
B:p=7 q=﹣18
C:p=﹣7 q=18
D:p=﹣7 q=﹣18
Our science teacher asked us ____ we ____ ever been in a maglev train.
胆固醇、小分子脂肪酸、维生素D等物质以简单扩散的方式优先通过细胞膜,这是因为