Consider statements about human immunity: 1. IgG is the most abundant antibody in blood. 2. IgE is involved in allergic reactions. 3. IgA is found in mucosal secretions. Which are correct? MCQ with Answer and Explanation

Explanation:
The heart is a muscular pump that circulates blood through the cardiovascular system, delivering oxygen and nutrients to tissues and removing waste. The lungs are the primary organs of the respiratory system, where gas exchange occurs: oxygen diffuses from the alveoli into the blood, and carbon dioxide diffuses from the blood into the alveoli to be exhaled. The kidneys are the primary excretory organs, filtering blood to remove metabolic waste, excess water, and ions, producing urine. All statements are correct.

Explanation:
Restriction endonucleases cut DNA at specific palindrome sequences, generating sticky or blunt ends, which can be ligated to vector DNA. This is the basis of genetic engineering. R explains A.

Explanation:
In aerobic respiration, oxygen accepts electrons at the end of the ETC, forming water. Without it, the chain would halt. This directly explains why oxygen is required.