Solution

In Equisetum, the gametophyte independent and hence gametophytes are not retained on the parent sporophytes. The spores germinate shortly after shedding and gives rise to prothallus.
Ginkgo is a living gymnosperm belonging to the group ginkgopsida also considered as a living fossil. In gymnosperms male gametophyte is dependent.
Riccia is the simplest sporophyte among bryophytes while Polytrichum is the highest evolved sporophyte.
Volvox is a green alga. Sexual reproduction in Volvox is oogamous. In this, female gamete is nonmotile and egglike and male gamete is motile.
Slime mold is an informal name given to several kinds of unrelated eukaryotic organisms that can live freely as single cells but can aggregate together to form multicellular reproductive structures. Spores in slime molds are unicellular and have smooth, spiny or reticulately thickened cell walls.
All the above statements are false except ' In Ginkgo, male gametophyte is not independent'.
So, the correct answer is 'one'.