请说出心尖部听到得心律性质（）
A.早搏
B.窦性心律不齐
C.窦性心动过速
D.正常心音
E.窦性心动过缓
参考答案：D
—Could you go to buy some salt for me, Vince?
—I'd love to, Mum, but I ________ my homework.[ ]
A. do
B. did
C. am doing
D. was doing
酶催化周期
