In animals which of the following body systems delivers nutrients and oxygen to cells
a. digestive system
b. respiratory system
c. excretory system
d. circulatory system

D. circulatory system
that is the answer.
The open circulatory system is found in arthropods and mollusks. The body cavity of these animals is called a hemocoel. The heart pumps a blood-like substance directly into the hemocoel where it moves freely and the organs are able to directly access the nutrients. In the hemocoel, blood and interstitial fluid (a special fluid which surrounds cells) is combined into a substance called hemolyph. This is the goo which sometimes squishes out of bugs when they get stepped on. 

The main role of dna in the  cell is the long-term storage of information. it is often compared to a blueprint, since it contains the instructions to construct other components of the  cell, such as  proteins  and rna molecules.the main function of rna is to carry information of amino acid sequence from the genes to where  proteins  are assembled on  ribosomes  in the  cytoplasm. mark brainliest, my work is good.

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