B. Covalent (Bond) I hope this helps! ^^
Plants release oxygen into the atmosphere during photosynthesis while respiration by plants and animals and the decomposition and decay of dead organisms releases carbon dioxide into the atmosphere. These three produce maintain a cycle in which plants and animals depend on and benefit from each other.
If the strand of Nucleic acid does not have a U - it must be DNA. Any sequence with a U is considered to be RNA. Therefore, CAGACT is considered to be a strand of DNA.
