Life cycle of Ectocarpus and Fucus respectively are:

Haplodiplontic cycle is the life cycle that is intermediate between haplontic and diplontic. In this, both the haplontic and diplontic are free-living and multicellular. In diplontic life cycle, the diploid sporophyte is dominant. Ectocarpus and Fucus are algae which have both haplodiplontic and diplontic life cycle. So, the correct answer is option D.