下列单体能在一定条件下发生加聚反应生成 的是( )
A:丙烯
B:2甲基1,3丁二烯
C:乙烯和丙烯
D:2甲基2丁烯
One valuable tip for graduates is that first impressions during a job interview really________.
用字母给下列句子排序。
A. I like my kite. It's nice.
B. Can I help you?
C. Thank you.
D. Here you are.
____ ____ ____ ____
数列{an}满足an=n,n=2k-1ak,n=2k,其中k∈N*,设f(n)=a1+a2+a3+...+a2n-1+a2n,则f(2013)-f(2012)等于( ).