List 3 positive things that humans use algae for:

Here's a few I got off google

#1: Algae Is Efficient to Create BioFuel.

#2: Algae Can Use Land That Would Otherwise Go to Waste.

#3: Algae Can Be Used for Animal Feed.

#4: Algae Can Function As An Energy Source.

#5: Algae Can Be Used To Create Vegetable Oil.

#6: Algae is a Great Human Food Supplement.

Use which ever ones you want