In angiosperm, the haploid, diploid and triploid structures of a fertilized embryo sac sequentially are:

Step-by-step solution

Synergids are pairs of haploid cells present at the micropylar end of embryo sac. Zygote which is a diploid structure undergoes divisions to form an embryo. Antipodal and polar nuclei are also haploid in nature. Primary endosperm nucleus is triploid in nature. In a fertilized embryo sac the haploid, diploid and triploid structures are synergid, zygote and primary endosperm respectively.