超声诊断成熟卵泡的标准是()①卵泡表面无卵巢组织覆盖②卵泡长径≥20mm③卵泡张力高,壁薄而光滑④子宫直肠窝少量积液
A.①
B.①②
C.①②③
D.①②③④
E.①③
参考答案:C
简述教育的本质特征。
I could speak ______ Japanese ______ Chinese, so I had to talk with him in English.
A. not only; but also B. both; andC. neither; nor D. either; or