What is the function of gerund in below sentence.
what i like is teaching.

Okay, biology isn't exactly my strongest subject (it never has been), but i'm pretty sure the answer is nucleotides. dna is made up of nucleotides. each nucleotide contains a phosphate group, a sugar group, and a nitrogen base. there are four different nitrogen bases: adenine (a), thymine (t), guanine (g), and cytosine (c). a always pairs with t, and g always pairs with c.

Afirefighter is a rescuer extensively trained in firefighting, primarily to extinguish hazardous fires that threaten life, property and the environment as well as to rescue people and animals from dangerous situations.  just cut some parts to make them shorter and add some of your facts or what describes them most. or what they are supposed to do.