A:his being not able
B:him not to be able
C:his not being able
D:him to be not able
若正项数列{an}满足lgan+1﹣lgan=1,且a2001+a2002+a2003+…+a2010=2015,则a2011+a2012+a2013+…+a2020的值为____ .
在四边形ABCD中,∠B=90°,AC=4,AB∥CD,DH垂直平分AC,点H为垂足,设AB=x,AD=y,则y关于x的函数关系用图象大致可以表示为( )