The main theme of the passage is
Option (a).
The author starts of the passage saying “the march of sex-selective abortion in Asia seems relentless”. He then moves on to tell that economic prosperity in fact has not resulted in improvement of sex ratio. In the last paragraph, he says “Both countries have been campaigning against sex-selective abortion for years. All, it seems, to no avail”. Hence option (a). The author does not state that sex- selective abortion is prevalent only in India and China.