Which of the following ions is an oxyanion? 1. f- 2.so42- 3.nh4+ 4.scn-

An anion is a negatively charged ion, meaning that the ion gained one or more electrons, thus became negatively charged.

An oxyanion is an anion that contains at least one oxygen atom bounded to other element(s)

Checking the choices given, we will find that the only oxyanion is:
(SO4)2- 

Well technically there are two correct answers b and d. but for you its probably b in general.good day sir/ma'am : ) (i know not gender)