Because the genetic backgrounds of twins are identical, researchers can conclude that variations in their behavior must be due to environmental factors.

Monozygotic

Explanation:

Monozygotic twins are formed by fertilization of single sperm and single egg but during cleavage process they separate out and serve as individual organisms. After their birth, environmental factors may influence variation in their behavior even though they were identical clones of each other. Thus, it may conclude that, environmental factors may influence variation among monozygotic twins.        

i think the answer is gold im not entirely sure

x would be the most and the least would be y because there are more fruit   and seeds than flock z has insects