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

Input: Consider Input: What two types of communication do both humans and birds use primarily?

Output: visual and auditory

Input: Consider Input: Exemplified by cesium, which ignites spontaneously in air, pure elements with a high metallic character tend to be very what?

Output: reactive

Input: Consider Input: What are organisms that eat just one type of food?
Output: specialists