Onions are stem modifications of which of the following types?

Onions are stem modifications of bulbs. Onions grow during a cold weather, but forms bulbs when the weather is warm. Onions can either be grown using seeds or through their bulbs. That is why, the stem modification of onions are bulbs. Tuber is from potatoes, whereas corm is from crocuses and gladioli.

They are stem modifications of bulbs