In some algae, the two gametes are so similar in appearance that:

It is not possible to categorize them into male and female gametes

The correct answer is Option (2)- It is not possible to categorize them into male and female gametes

Gametogenesis refers to the process of formation of the two types of gametes – male and female. Gametes are haploid cells. In some species of algae, the gametes produced are isogamous, meaning that the gametes are morphologically similar or identical. This means that they look so similar that they cannot be distinguished as male or female based solely on their appearance. Unlike in higher organisms where male and female gametes can be differentiated by their size or structure (e.g., sperm and egg cells), isogamous gametes do not have such distinctions. Therefore, it is not possible to categorize them into male and female gametes based on their appearance alone.

However, in a majority of sexually reproducing organisms the gametes produced are of two morphologically distinct types (heterogametes). In such organisms the male gamete is called the antherozoid or sperm and the female gamete is called the egg or ovum