The muscular tube that connects the pharynx to the stomach is the: MCQ with Answer and Explanation

Explanation:
Vitamin A is essential for the synthesis of rhodopsin, a visual pigment; its deficiency leads to night blindness, the inability to see in low light. Vitamin B1 (thiamine) is crucial for carbohydrate metabolism; its deficiency causes beriberi, characterized by nerve and heart dysfunction. Vitamin C deficiency causes scurvy, characterized by bleeding gums and poor wound healing; rickets is caused by a deficiency of Vitamin D, leading to soft, weak bones in children. Thus, statements 1 and 2 are correct.

Explanation:
Hemoglobin has a much higher affinity for oxygen than for carbon dioxide; it binds O2 readily in the lungs. Inside RBCs, the enzyme carbonic anhydrase rapidly catalyzes the conversion of CO2 and water into carbonic acid. Approximately 70% of CO2 is transported in the blood as bicarbonate ions in the plasma. Thus, statements 2 and 3 are correct.

Explanation:
Thermoregulation uses negative feedback mechanisms: when body temperature rises, sweating and vasodilation cool the body; when it falls, shivering and vasoconstriction generate and conserve heat. Negative feedback counteracts deviations from a set point. Positive feedback amplifies a change (e.g., labor contractions).