a predator population suddenly decreases even though the prey population stays the same. Besides disease, what could explain this change?

hunting, the predator is in the middle of the food chain

Explanation:

hunting can WIPE OUT species as shown by the dodo bird in the past.

food chains often work as 1-2-3 or 1-2-3-4 in levels.

The synonym for genetic engineering is B. recombinant DNA technology. If you are recombining something, it means that you are modifying it, changing it so that you can create something new. This is what genetic engineering is all about - you take the qualities you want, and combine them in order to create a new "being."