A $500 investment and a $1, 500 investment have a combined yearly return of 8.5 percent of the total of the two investments. If the $500 investment has a yearly return of 7 percent, what percent yearly return does the $1, 500 investment have ？（）

A.A

B.B

C.C

D.D

E.E

消石灰（熟石灰）的主要化学成份是（）。

A、C、A、O

B、C、A、（OH）2

C、C、A、C、O3

D、C、A、SO4