. Open circulatory system is present in
A: Annelids and chordates
B: Annelids and arthopods
C: Arthropods and chordates
D: Arthropods and Mollusca
An open circulatory system is depicted by the mixing of blood and interstitial fluid in an organism.
The two largest phyla i.e., Mollusca and Arthropoda possess an open circulatory system.
Hence, option D. i.e., Arthropods and Mollusca is the correct answer.