Given a scientific question, generate a correct answer to it.

Input: Consider Input: Negative feedback controls insulin secretion by what organ?

Output: pancreas

Input: Consider Input: Overproduction of offspring, combined with limited resources, results in what?

Output: competition

Input: Consider Input: What category of elements are chacterized by their ability to reflect light, called luster, their high electrical and thermal conductivity, their high heat capacity, and their malleability and ductility?
Output: metals