多囊卵巢综合征患者行诊断性刮宫时机应选择在（）

A.月经第4日

B.月经干净后3～5日

C.在月经前数日或月经来潮6小时内

D.月经第2日

E.无特殊要求

All the parents in Mianyang admire Nanshan Middle School         the teachers are treating their students like friends.

A．why

B．where

C．that

D．which