Gmat数学,求简便算法~~For every integer k from 1 to 10, inclusive, t

Gmat数学,求简便算法~~
For every integer k from 1 to 10, inclusive, the kth term of a certain sequence is given by . If T is the sum of the first 10 terms in the sequence, then T is
(A) greater than 2
(B) between 1 and 2
(C) between 1/2 and 1
(D) between 1/4 and 1/2
(E) between 1/4
the kth term of a certain sequence is given by （-1）^(k+1)乘以(1/2^k)