What is a basic difference between a sporophyte and a gametophyte?

a sporophyte is a reproductive structure while a gametophyte is not.
a sporophyte undergoes sexual reproduction while a gametophyte undergoes asexual reproduction.
a sporophyte is part of the diploid phase while a gametophyte is part of the haploid phase of the plant life cycle.
a sporophyte is much smaller than the gametophyte.

The correct answer is -  A sporophyte is part of the diploid phase while a gametophyte is part of the haploid phase of the plant life cycle.

Gametophyte is the haploid phase of plants which bears sex organs. It forms gametes and gametes after fusion forms zygote. Zygote is diploid which develops into the sporophyte thus, sporophyte phase is diploid. Sporophyte bears sporangia which produces haploid spores after meiosis. Spores germinate to form haploid gametophytes.

because the light is a great source of energy for the plants to survive. (i hope this )