Which generation is dominant in the life cycle of a horsetail?

A) haploid gametophyte
B) diploid gametophyte
C) haploid sporophyte
D) diploid sporophyte
E) monoploid sporophyte

The dominant generation in the life cycle of a horsetail is the diploid sporophyte generation. This generation produces sporangia, which in turn produce haploid spores. The spores grow into the small, independent gametophyte generation which produces gametes. Fertilization of these gametes results in the formation of a diploid zygote, which grows into the dominant sporophyte generation once again.