All people, ________ they are old or young, rich or poor, have been trying their best to help those in

need since the disaster.[ ]

A. even if  

B. whether

C. no matter  

D. however

肌牵张反射使（）。

A．受牵拉的肌肉发生收缩

B．同一关节的协同肌发生抑制

C．同一关节的拮抗肌发生兴奋

D．伸肌和屈肌都收缩

E．受牵拉的肌肉发生舒张