An average of just 18.75cm of rain fell last year, making ______ the driest year since California became a state in 1850.

A．each

B．it

C．this

D．one

正常人钙、磷（mg/dl）乘积为（）。

A.16～20

B.26～30

C.36～40

D.46～50

E.56～60