Which one of the following is hetero-sporous?

Most pteridophytes produce only one kind of spores and are called homosporous.
A few genera produce two kinds of spores, small microspores and large macrospores (megaspores); they are called heterosporous.
Selaginella and Salvinia are the common examples of heterosporous pteridophytes.
The microspores and megaspores germinate to give male and female gametophytes respectively, and the female gametophyte is retained on the parent sporophyte for some time.
This event is considered a precursor to the seed habit, an important step in evolution.
Adiantum, Equisetum and Dryopteris are homosporous.
So the heterosporous plant is Salvinia.