Correct Answer: A

Rationale: The correct answer is 'Solid.' Solids have particles that are tightly packed together in a fixed pattern, allowing them to vibrate in place. This highly organized structure gives solids a definite shape and volume. In contrast, liquids have particles that are close together but can move past each other, enabling them to flow and take the shape of their container. Gases have particles that are far apart and move freely in all directions, filling the entire space available to them. Plasmas, on the other hand, have highly energized particles that do not have a fixed pattern and are not confined by a definite volume or shape.

Correct Answer: A

Rationale: The correct answer is A: Nephron. The nephron is the functional unit of the kidney responsible for waste removal and blood volume regulation. It is composed of several structures, including the glomerulus, Bowman's capsule, proximal convoluted tubule, loop of Henle, distal convoluted tubule, and collecting duct. The other options mentioned in the question (ureteric bud, renal pyramid, and glomerulus) are not the correct names for the microscopic filtering unit within the kidney. The glomerulus is a part of the nephron, specifically responsible for ultrafiltration in the initial stage of urine formation.

Correct Answer: A

Rationale: Mass is a measure of the amount of matter in an object and remains constant regardless of changes in gravity. Weight, on the other hand, is a measure of the gravitational force acting on an object and varies with changes in gravity. Volume is the amount of space occupied by an object and can change with changes in gravity. Density is the mass of a substance per unit volume and can also change with changes in gravity if the volume changes. Therefore, the correct answer is mass as it remains the same regardless of the gravitational force acting on the object, making it an intrinsic property of the substance.

Correct Answer: C

Rationale: Oligodendrocytes are a type of glial cell that provides structural support and insulation for neurons in the central nervous system by forming myelin sheaths around axons. Schwann cells (option A) perform a similar function but in the peripheral nervous system. Astrocytes (option B) are involved in providing nutrients to neurons, maintaining the chemical environment, and repairing damage. Microglia (option D) are primarily responsible for immune defense in the central nervous system, not for providing structural support and insulation for neurons.

Correct Answer: C

Rationale: The correct answer is the pancreas. The hormone responsible for regulating blood sugar levels is insulin, which is produced by the pancreas. The pituitary gland produces various hormones that regulate other endocrine glands, the thyroid gland produces hormones that regulate metabolism, and the adrenal glands produce hormones involved in the stress response. Therefore, choices A, B, and D are incorrect in the context of regulating blood sugar levels.