The correct option is B Cladophora
When the fusing gametes are similar in their appearance and cannot be categorised as male and female gametes then they are called homogametes/isogametes. Example: Cladophora (algae).
Fucus, Cycas and human beings produce heterogametes as the gametes that fuse during fertilisation are morphologically distinct, i.e., these gametes differ in structure. The male gamete is called the antherozoid or sperm and the female gamete is called the egg or ovum.