At that time we lived in houses which _______ old, cold and unsafe.  [ ]

A. are          

B. were          

C. is              

D. was

以下程序运行后的输出结果是 【4】 。
main()
char c; int n=100;
float f=10; double x;
x=f* =n/=(c=50)；
printf("%d %f\n",n,x);