The number of people who____left the island ____reached 10,000.[ ]

A. has, has

B. have, have

C. has, have

D. have, has

延安市环境监测部门常采用五氧化二碘(化学式为I₂O₅)来测定空气中的一氧化碳含量。五氧化二碘中碘元素的化合价为 ( )               

A．-5

B．+5

C．+3

D．+2