![](https://cos-cdn.shuashuati.com/pipixue-wap/2020-1230-1107-56/ti_inject-812ce.png)
The opening of atrioventricular valve can be seen in: ()
A.
isovolumic shrinkage at the end of the period
B.
ventricular systolic period beginning
C.
isovolumic diastolic period beginning
D.
isovolumic systolic period beginning
E.
isovolumic diastolic period end