适用以铸铁、铜合金为主的铸造是（）。
A.砂型铸造
B.熔模铸造
C.离心铸造
D.压力铸造
参考答案：C
I felt _____ my heart would burst with joy when I heard the news that Chang'e I was sent up successfully
to turn around the moon. [ ]
A. even if
B. if only
C. as if
D. only if
设函数f(x)的傅氏级数的和函数为
其中
，则S(-9)=______．
，则S(-9)=______．