下蹲控制姿势不变股四头肌的收缩形式是（）。
A.等长收缩
B.等张收缩
C.离心收缩
D.向心性收缩
E.等动收缩
参考答案：C
_____ you may have, you should gather your courage to face the challenge. [ ]
A. However a serious problem
B. What a serious problem
C. However serious a problem
D. What serious a problem
有机养殖场引入的常规种公畜只要在引入后严格按照有机方式饲养，可以不要求其经历转换期。
