Which of the following statements is the best description of the life cycle of plants such as ferns?
plants have a two-part life cycle, spending part of their life in a diploid phase and part in a haploid phase.
plants have a single life cycle and are entirely diploid.
plants have a single life cycle and are entirely haploid.

The answer is Plants have a two-part life cycle, spending part of their life in a diploid phase and part in a haploid phase.

Let's, for example, take fern life cycle. Their life cycle has alternation of generations - a haploid gametophyte and a diploid sporophyte. Gametophyte produces haploid gametes which fuse to form a diploid zygote. Therefore, gametophyte reproduces with gametes. The zygote grows into diploid sporophyte which produces haploid spores. Sporophyte reproduces with spores, and new gametophyte develops. 

1 red : 2 orange : 1 yellow