Assertion :In angiosperms, endosperm development precedes embryo development. Reason: Double fertilisation ensures that the nutritive tissue is formed before the zygote starts cleaving so that the energy spent on the formation of endosperm does not get wasted.

The correct option is A Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

During double fertilisation in angiosperms, one male gamete fuses with the egg to form the diploid zygote (syngamy or generative fertilisation). The diploid zygote finally develops into embryo. The other male gamete fuses with the two polar nuclei(or secondary nucleus) to form the triploid primary endosperm nucleus, PEN (triple fusion or vegetative fertilisation). double fertilisation ensures that the nutritive issue is formed before the zygote starts cleaving so that the energy spent on the formation of endosperm does not go waste in case the fertilisation fails. Angiosperms are therefore, economical and more specialised as compared to gymnosperms where a large nutritive female gametophyte is formed long before fertilisation.

So, the correct answer is 'Both Assertion and Reason are correct and Reason is the correct explanation for Assertion'.