How Does Genetic Screening of Embryos Lead to Skewed Sex

How does genetic screening of embryos lead to skewed sex ratios in some countries?

A) Most commonly, in countries where girls are seen as more valuable to a family, male embryos are terminated more frequently.
B) Most commonly, in countries where boys are seen as more valuable to a family, female embryos are terminated more frequently.
C) In some countries, female embryos are routinely destroyed by law.
D) In some countries male embryos are routinely destroyed by law.
E) It would be unethical to favor male or female children, so this doesn't happen anywhere.