In respect of classification of algae, the members of Phaeophyceae are commonly called:

brown algae

The correct answer is Option (3) -brown algae

In the classification of algae, the members of Phaeophyceae are commonly called brown algae.

Brown algae are a diverse group of multicellular algae characterized by their brown or olive-green color, which results from the presence of the pigment fucoxanthin. They are predominantly marine organisms and are commonly found in colder coastal waters. Brown algae exhibit a wide range of forms, from small filamentous species to large, complex structures such as kelp forests. They play important ecological roles as primary producers and provide habitat and food for various marine organisms.