如图所示，两个同心放置且共面的金属圆环，条形磁铁穿过圆心且与两环平面垂直，通过两环的磁通量Φ_a、Φ_b比较，则（　　）

A．Φ_a＞Φ_b

B．Φ_a＜Φ_b

C．Φ_a=Φ_b

D．无法确定

For the child experiencing excessive vomiting secondary to pyloric stenosis, the nurse should assess the child for which of the following acid-base imbalances

A．Respiratory alkalosis.

B．Respiratory acidosis.

C．Metabolic alkalosis.

D．Metabolic acidosis.