I didn't understand ______ so I raised my hand to ask. [ ]

A.what my teacher says

B.what does my teacher say

C.what my teacher said

D.what did my teacher say

女性，39岁，因口腔黏膜反复起疱9个多月就诊，起疱与进食无关，疱损可破溃形成溃疡。临床检查可见上下牙唇颊侧牙龈黏膜有多个水疱或糜烂面，探针无法探入疱损周围黏膜下，左侧舌腭弓黏膜有瘢痕挛缩，患者不曾用过任何抗免疫治疗。关于该疱损的说法下列哪项可能是错误的

A．应取话检确诊

B．直接免疫荧光检查有助于诊断

C．还应检查皮肤和眼结膜

D．水疱位于上皮下

E．水疱位于上皮内