The answer is septum.
Frog hearts have 3 chambers - one ventricle and two atria. The left atrium receives oxygenated blood, and the right atrium receives deoxygenated blood and they both empty into the ventricle. Since there is only one ventricle, oxygenated and deoxygenated blood will mix. If there would be a septum in the ventricle, similar to those in lizards, less mixing will occur. Anyway, in frog's ventricle, there is a ventricular fold that prevents complete mixing of oxygenated and deoxygenated blood.
Answer: answer below.
Explanation: Research for crude oil is also known as Petroleum.
Answer: Topoisomerases (or DNA topoisomerases) are enzymes that participate in the overwinding or underwinding of DNA. The winding problem of DNA arises due to the intertwined nature of its double-helical structure. During DNA replication and transcription, DNA becomes overwound ahead of a replication fork.
Explanation: