Which is diploid structure?

•Pollen grains develop from microspores. Microspores are formed from the microspore mother cell. Microspore mother cell is diploid and undergoes meiosis to produce four haploid microspores which develop to form pollen grains. Hence, pollen grains are haploid.
•Egg is the female gamete present in the embryo sac. Egg cell is haploid and on fusion with male gamete produces a diploid zygote. Hence, egg is haploid.
•Megaspore is formed from the megaspore mother cell. Megaspore mother cell is diploid and undergoes meiosis to produce four haploid megaspores. Hence, megaspore is haploid.
•MMC or Megaspore Mother Cell is a diploid cell which develops in the Nucellus of the ovule. MMC undergoes meiotic division to produce four haploid megaspores out of which, only one remains functional and the other three degenerate.
Hence, only MMC is diploid and rest are haploid structures.