目前影响健康最重要的因素是（）
A.自然环境
B.社会环境
C.行为因素和生活方式
D.生物学因素
E.遗传因素
参考答案：C
You are performing two sums: the first is a sum of two scalar variables and the second is a matrix sum of a pair of two- dimensional arrays-size 1000 by 1000. What speedup is achieved when the calculations are performed on size 1000 processors
A．50
B．100
C．999
D．none of the above
用煤气的加热设备与风机之间应设安全联锁、紧急切断装置,严防煤气倒灌爆炸事故。（）
