You are given a sentence and your task is to generate another sentence that supports the given input.

[EX Q]: Composed mainly of hormone-producing chromaffin cells, the adrenal medulla is the principal site of the conversion of the amino acid tyrosine into the catecholamines epinephrine, norepinephrine, and dopamine.
[EX A]: Catecholamines are a class of amine hormones that when synthesised form the amino acid tyrosine.

[EX Q]: Weather fronts mark the boundary or transition zone between two air masses and have an important impact upon the weather.
[EX A]: In weather terms, the boundary between two air masses is called front.

[EX Q]: Active galaxies usually fall in three types;
[EX A]:
There are three types of galaxies.