Option D – seed plants reproduce without standing water
Step-by-step explanation:
The unique feature that distinguishes seed plants from mosses is the adaptability of seed plants to reproduce even on dry lands without standing water.
The completion of the lifecycle of a moss (bryophyte) requires water for the sperms released by the male gametophytes to swim. The sperm propels its flagella through the water and reaches the female gamete or egg to fertilize and divide to form new gametophytes.
The pollen grains of the male gametes are the main adaptive structures that aid the seed plants to reproduce without water and to evolve and grow in multitude compared to the mosses. The pollen grains with the haploid cells encased in protective coat can disperse and travel far off from the sporophyte from which they originated and fertilize female gamete there to produce new gametophytes.