Plants alternate their generations by switching between

Plants alternate their generations between sporophyte and gametophyte generations.

Explanation:

Plants life cycle has two generations i. e. Sporophyte and gametophyte. Sporophyte is the first phase of plant life cycle in which spores are produced that are diploid i. e. double number of chromosomes while the second phase is gametophyte in which gametes are produced that are haploid i. e. half number of chromosome. Gametes contains sperm cells and egg cells which fuse together in the process of fertilization.