(1) is not correct because if they were identical twins they would be the same sex. (2) is not a valid reason. (4) is not correct. Thus, (3) is the correct option. The answer also corresponds to option (1) and why it's incorrect. If they were identical twins, they would not be both a female and male...
Becuase the chemicals can only work for a little in the pesticides so when bad weather comes around it finishes the rest of the chemicals in the pesticide.
