Ann wants a bike her birthday present this year.
A:to
B:at
C:as
D:on
The bus got ________ in the snow and we had to walk the rest of the way.
已知i为虚数单位,复数z=1+2i1-i,则复数z的虚部是( )
等差数列{an}共有2n+1项,其中奇数项之和为4,偶数项之和为3,则n的值是( )