21.   Supoj said the planting of rice varieties that do not have a natural resistance to pests and fewer predators have contributed to the rapid rise in numbers of hoppers.

22.   When it involves an area of conflict in which there are already natural resistance, it becomes more difficult.

23.   Baboons have a natural resistance to the virus that causes AIDS.

24.   Baboons have a natural resistance to the virus that causes AIDS, a resistance doctors have not yet explained.

25.   Doctors and researchers do not know why the baboon has a natural resistance to the AIDS virus.

26.   They hope the transplant from baboons, which have a natural resistance to the HIV virus, would boost his immune system against the disease.