据腾讯官网报道,截2011年3月,“QQ空间”活跃帐户数达到428000000,比上一季度增长10.4%,这里的428000000用科学记数法表示为: .
4.28×108
解:
_____his father had come, his face lit up.
A.Having learned
B.When he learned
C.Heating
D.When learning
锅炉效率计算时须考虑哪几项热损失?