Which of the following types of algae would have rigid cell walls composed of silica?
a. paramecium
b. euglena
c. diatoms
d. spyrogyra

Where is having brightly colored feathers that attract mates most clearly an adaptation for a bird? a. a forest with dense vegetation b. a sandy beach beside an ocean c. a snowy tundra with little vegetation d. a swamp with many hawks that eat birds