Answer:
4. alternation of generations
Step-by-step explanation:
The attribute that is common to true mosses, ferns, and spike mosses is the switch in their life cycles between the diploid generation and haploid generation, a process known as alternation of generation.
Mosses, ferns and spike mosses are able to reproduce sexually through alternation of generation.
The haploid male and female gametophytes fuse together during fertilization to give a diploid zygote which divides through mitosis to give a diploid sporophyte. The reproductive cells of a mature sporophyte divides to give rise to haploid gametes or gametophytes and the cycle continues.
The correct option is option 4.