What does that sign mean?    

     [ ]

A. It means you must keep the grass

B. It means you must keep off the grass

C. They mean you shouldn't keep off the grass

D. They mean you should keep the grass

关于血清氨基转移酶的描述，不正确的是（）。

A.受损时活性迅速增加

B.AST主要存在于线粒体中

C.ALT主要存在于线粒体中

D.重症肝炎时，AST>ALT

E.ALT反映肝细胞损伤的灵敏度高于AST