The organism that causes citrus canker is: MCQ with Answer and Explanation

Explanation:
Nitrous acid (HNO₂) is a chemical mutagen that can deaminate bases (e.g., cytosine to uracil), causing base-pair changes and mutations. X-rays, UV radiation, and gamma rays are physical mutagens (ionizing and non-ionizing radiation). Chemical mutagens include base analogs, alkylating agents, and intercalating agents. Mutagens increase the rate of mutations beyond natural levels.

Explanation:
Pneumothorax is the accumulation of air in the pleural space, causing lung collapse. Pneumonia is lung infection, emphysema is alveolar damage, pleurisy is inflammation of pleura. It can be spontaneous or traumatic.

Explanation:
The right atrium receives deoxygenated blood from the systemic circulation via the superior and inferior vena cavae. It pumps blood to the right ventricle. The left atrium receives oxygenated blood from the lungs, the left ventricle pumps to the body, the right ventricle to the lungs.