Alternation of generations means that plants produce:

only haploid multicellular organisms

only diploid multicellular organisms

only diploid multicellular organisms with single-celled haploid gametes

both haploid and diploid multicellular organisms

Alteration of generations means that plant produce both haploid and diploid multi-cellular organisms

Explanation:

Alteration of generations has 2 stages, gametophyte and sporophyte

The gametophyte stage is the haploid (n) stage, where gametes are produced in preparation for fertilization. The sporophyte stage is the diploid stage (2n) where fertilization occurs.