Answer:
D) begins as a cell, comes from an organ, is part of a system
Step-by-step explanation:
Here is how pollen is formed, in simpler words, it comes from sporogenic tissue, formed inside the male organ called the anther, and is part of the male reproductive system.
The formation of a pollen grain begins inside the male part of a flower called the anther, within specific tissue called sporogenic tissue. Here, the developing pollen receives nutrition and a coat of cellulose, which is a very strong plant protein. First, large pollen mother cells are produced, which eventually break into individual pollen grains through cell division. At this point, the pollen grain gets its outer coat, called the exine, which is made from another tough plant protein. The exine protects the delicate genetic material inside the pollen grain from water loss, and damage caused by UV radiation and other environmental causes. In some plants, the pollen grain also gets a sticky outer layer to help it adhere to the female part of another plant, called the stigma. The final step involves another cell division, which creates two cells within one pollen grain. After that, the pollen grains move to a drying-out phase, after which they take on their dusty appearance and are ready to go out into the world and fertilize ovules.