Many Algal Species Have Life Cycles Consisting of Alternating Haploid

Many algal species have life cycles consisting of alternating haploid and diploid generations. Which sentence describes the organisms that comprise the most common life cycle in brown algae?

A) They are unicellular in both the haploid and diploid stages.
B) They are colonial in both the haploid and diploid stages.
C) They are multicellular in both the haploid and diploid stages.
D) They are multicellular in the haploid stage and unicellular in the diploid stage.