What structure in seed plants contains the sporophyte and is often classified as multicellular and complex?

The seed is a crucial structure in seed plants, as it contains the sporophyte generation, which is the dominant phase in the life cycle of vascular plants. A seed is multicellular and complex because it is made up of tissues that develop from the fertilized ovule. This includes the young sporophyte (embryo), the stored food (endosperm), and protective layers (seed coat) that provide insulation and defense against environmental factors.

Seeds are designed to protect and nourish the developing embryo until conditions are favorable for germination. The complex structure is essential for the plant's successful reproduction and adaptation to various environments. Other options such as fruit, spore, and pollen do not encapsulate a complete sporophyte; fruit surrounds seeds but does not contain the sporophyte itself, spores are single-celled and represent the gametophyte generation in the plant life cycle, and pollen grains are male gametophytes that facilitate fertilization but do not contain the embryo. Thus, the seed's role as a multicellular, complex structure containing the sporophyte distinguishes it in the life cycle of seed plants.