房性期前收缩多呈不完全性代偿间歇的原因是（）。

A.窦房结节律重整

B.房室传导阻滞

C.窦房阻滞

D.异位搏动距窦房结较远

E.窦性心律不齐

The primary motivation for investing in commodity-linked bonds is that they most likely provide:（）

A. an income stream.

B. capital gains returns.

C. protection against interest rate risk.