题型:选择题 He is always able to make us _____ in class. We usually feel happy while learning English. [ ]A. laugh B. to laugh C. laughing D. to laughing 查看答案
题型:单项选择题 A1/A2型题 乳腺癌的多普勒血流特点是()A.血流丰富,频谱为高速高阻型B.血流丰富,频谱为高速低阻型C.血流不丰富,频谱为高速高阻型D.血流不丰富,频谱为高速低阻型E.血流丰富,频谱为波浪状宽带型 查看答案