During one of our English language classes, we came across this sentence where we needed to cross the wrong word out:
The statistics, carried out by a university, reveals that two-thirds of the adult population suffer from unemployment, one of the most important city phenomenon/phenomena.
Some students said the singular phenomenon should be crossed out, but the teacher said the plural phenomena should be instead, so the correct answer was "one of the most important city phenomenon". Why? As I know, when we say "one of the X" we use a plural word. Is it not correct? I searched this online but I'm still really confused, please explain thoroughly.