A.......

sorry....I forgot the half which I had taken common....so that answer would be 7/15...

take 1/2 common and write 2 in the numerator of the corresponding terms.....
then write 2/3 as 1-1/3
2/15 as 1/3-1/5
2/35 as 1/5-1/7 and so on.....
the corresponding terms cancel out and you are left with 1-1/15
so the answer would be 14/15...