Which of these is unique to flowering plants? haploid gametophytes, an embryo surrounded by nutritive tissue, double fertilization, a dominant sporophyte generation, pollen production

double fertilization

Explanation:

Flowering plants or angiosperms are seed-producing plants with the ability to produce reproductive organs-flowers and fruits with seed in it (unlike gimnosperms which contain naked seed). Another distinctive feature of angiosperms is their reduced gametophytes. This feature most likely reduces the time between pollination and fertilization. Fertilization in flowerin plants is double, meaning that two sperm cells fertilize ovule cells (egg cell and central nuclei cell) : one forms diploid zygote which will develop in embryo, while other form triploid cell which will develop into endosperm (provides nutrition for the embryo).