Correct Answer: A

Rationale: The correct order of joint types, from least mobile to most mobile, is hinge, condyloid, saddle. A hinge joint allows movement in one plane (like a door hinge), a condyloid joint allows movement in two planes but not rotation (like the wrist), and a saddle joint allows movement in multiple directions (like the thumb). Choice A, 'Hinge, condyloid, saddle,' is the correct sequence as it accurately represents the order of increasing permitted motion in joints. Choices B, C, and D are incorrect because they do not follow the correct order of joint types from least mobile to most mobile as required by the question.

Correct Answer: B

Rationale: The correct answer is B: Secondary. The secondary structure of a protein is defined by the folds and coils of the protein's polypeptide backbone. This level of structure is characterized by the formation of alpha helices and beta sheets, which are stabilized by hydrogen bonds between amino acids along the polypeptide chain. Choice A, Primary, refers to the linear sequence of amino acids in the protein. Choice C, Tertiary, involves the 3D folding of the entire polypeptide chain. Choice D, Quaternary, pertains to the arrangement of multiple polypeptide subunits in a protein complex.

Correct Answer: A

Rationale: The correct order of joint types, from least mobile to most mobile, is hinge, condyloid, saddle. A hinge joint allows movement in one plane (like a door hinge), a condyloid joint allows movement in two planes but not rotation (like the wrist), and a saddle joint allows movement in multiple directions (like the thumb). Choice A, 'Hinge, condyloid, saddle,' is the correct sequence as it accurately represents the order of increasing permitted motion in joints. Choices B, C, and D are incorrect because they do not follow the correct order of joint types from least mobile to most mobile as required by the question.

Correct Answer: C

Rationale: The correct answer is C, the glomerulus. The glomerulus is a cluster of capillaries in the kidney responsible for filtering blood as it enters the nephron. It plays a crucial role in the initial stages of urine formation by filtering waste products and excess substances from the blood. Choice A, the Bowman's capsule, is incorrect as it surrounds the glomerulus and captures the filtrate. Choice B, the Loop of Henle, is incorrect as it is part of the nephron responsible for water reabsorption. Choice D, the nephron, is incorrect as it comprises the functional unit of the kidney and includes the glomerulus, Bowman's capsule, and other structures.

Correct Answer: A

Rationale: The correct way to represent 8,600,000,000,000 in scientific notation with two significant figures is 8.6 x 10^12. Scientific notation involves expressing a number as a decimal (with one non-zero digit before the decimal point) multiplied by a power of 10. In this case, 8,600,000,000,000 is correctly written as 8.6 x 10^12 to maintain two significant figures and the appropriate magnitude. Choice B (8.6 x 10^-12) is incorrect as it represents a very small number due to the negative exponent. Choice C (8.6 x 10^11) is incorrect as it does not account for the magnitude of the original number. Choice D (8.60 x 10^12) is incorrect because it unnecessarily adds a zero after the decimal point, which is not warranted by the original number's precision.