What condition is most necessary to build a glacier?

The most necessary condition to build a glacier is: More snow must fall in the winter than melts in the summer.
when More snow fall in the winter than it melts in the summer, the snow will start to accumulate on the top of the higher terrain. This accumulation will form an abundant amount of snow on higher terrain, which will fall as glacier as soon as its temperature drop.

The answer would be a) -80of