In angiosperms, pollen grains are (1 point)

a. diploid, and are made when haploid gametes join in fertilization.
b. diploid, and are made when haploid gametophytes join in pollination.
c. haploid, and are made when haploid spores undergo mitosis.
d. haploid, and are made when haploid ovules undergo meiosis.

The answer is C. haploid, and are made when haploid spores undergo mitosis. 

Pollen grains are male gametophytes in plants. In pollen sacs of an anther, spore mother cells, which is diploid, undergo meiosis and form four haploid spores. These haploid spores undergo mitosis and form haploid pollen grains.

Through the process of elimination:
- Pollen grains are haploid, so choices A. and C. are eliminated.
- In ovules, female gametes are produced, not male gametes, so, choice D. is also eliminated.

The answer is ozone layer.