有关血管源性脑水肿，下列说法错误的是（）

A.病理生理基础是血脑屏障破坏，血浆进入细胞和间隔。 

B.主要发生在脑皮质。 

C.可见于肿瘤、出血、炎症等。 

D.在T1加权像显示不明显。 

E.Gd—DTPA增强后无异常对比增强。

Only when class began _____ that he had left his book at home. [ ]

A. will he realize

B. he did realize

C. did he realize

D. should he realize