A Only one variable changed
Answer:
genetic modification competitors increase
Explanation:
The fish developed the gills because of <em>genetic modification</em>. Because the fish are now able to swim in deep water, their <em>competitors</em> in shallower water will have less food. Likewise, competition for food among deep-water fish that eat the same types of food will <em>increase</em>.
The type of operations used for transforming plaintext to cipher text, the number of keys used, and the way in which the plaintext is processed.
Layers of fossils in pillars, the rock covering them is dated and we get an exact time of each layer.