When he arrived at the airport, Lee Minho found that ________ fans were waiting for him there.
A:hundred
B:hundreds
C:hundred of
D:hundreds of
如图所示是硫和铁丝分别在氧气中燃烧的实验示意图。这两个反应( )
下列说法中,正确的是( )
圆C的方程为(x﹣2)2+y2=4,圆M的方程为(x﹣2﹣5cosθ)2+(y﹣5sinθ)2=1(θ∈R),过圆M上任意一点P作圆C的两条切线PE,PF,切点分别是E,F,则PE→·PF→的最小值是( )