What do all plant life cycles have in common

Diploid and haploid phases alternate.

Explanation:

The life cycle of all plants has alternating diploid and haploid phases. In haploid phases (n) plants have only half the number of chromosomes in the diploid phase (2n). During the haploid phases the plant form is called gametophyte and in the sporophyte diploids, so we have the gametoophytic generations in the haploid phase and the sporophytic generations in the diploid phase.

i think a) betsy can donate only blood to mark is correct because, mark and betsy have the same blood type. whereas nobody else has b+ blood so betsy can't donate to them.

where is the scientific experiment?