Name an animal that is a member of the phylum cnidaria, an animal of the phylum arthropod, and an animal of the phylum echinoderm.

Astudent poured a solution of bromothymol blue indicator into three test tubes. then he placed an aquatic plant in two of the test tubes, as shown below. he placed a stopper on each test tube and placed them all in the dark for 24 hours. bromothymol blue turns from blue to yellow in the presence of co2