发生电火灾时，首先必须切断电源，然后救火和立即报警。
参考答案：对
（ ）既是25的因数，又是25的倍数。
The IPCC announcement three years ago that "most of the warming observed over the last 50 years is" ______.
A．possibly due to human activities
B．possibly because human activities
C．due to likely human activities
D．human activities likely attributable
