Final answer:
The lineage of green algae leading to multinucleate, multicellular organisms is Chlorophyta, which includes both unicellular and multicellular species with plant-like characteristics such as having chlorophyll a and b.
Step-by-step explanation:
The lineage of green algae leading to multinucleate, multicellular green algae is B) Chlorophyta. This diverse group includes not only unicellular species like Chlamydomonas, but also multicellular organisms such as Ulva. Characteristics shared with plants include the presence of chlorophyll a and b, cellulose cell walls, and the storage of carbohydrates as starch. However, green algae differ in that most are not multicellular or they exhibit less cellular differentiation compared to land plants. While some systems place green algae in the Protist Kingdom, modern treatments often omit the Kingdom level, categorizing green algae such as Caulerpa taxifolia, which can be multinucleate and exhibit complex structures within a single cell framework, in a separate phylum distinct from land plants.