Correct Answer: D

Rationale: The correct answer is D. Positive correlation indicates that as one variable increases, the other variable also increases. In this case, when plotting a comparison of rainfall to plant length, if the line trends to the upper right, it shows a positive correlation where as rainfall increases, plant length also increases. Choices A, B, and C show either no correlation or negative correlation, as they describe scenarios where the variables move in different or opposite directions.

Correct Answer: D

Rationale: The vas deferens is a duct that connects each testis to the urethra, allowing the transport of sperm. Choice A is incorrect because the vas deferens does not produce fluid to increase sperm mobility. Choice B is incorrect as the vas deferens is not a site for egg maturation. Choice C is incorrect as the vas deferens does not help control urine flow, its primary role is in the transport of sperm.

Correct Answer: C

Rationale: The correct answer is IgG. IgG is the only antibody that can cross the placenta, providing passive immunity to the developing fetus. IgA, IgD, and IgM do not cross the placenta. IgA is mainly found in mucosal secretions, IgD is involved in the activation of B cells, and IgM is the first antibody produced in response to an infection, but it does not cross the placental barrier.

Correct Answer: D

Rationale: Glucose is a monosaccharide, which is a simple sugar and not a macromolecule. Glycoproteins, DNA, and phospholipids are all examples of biological macromolecules. Glycoproteins are proteins covalently bonded to carbohydrates, DNA is a nucleic acid, and phospholipids are lipids that contain a phosphate group.

Correct Answer: B

Rationale: During photosynthesis, 12 molecules of NADPH and 18 molecules of ATP are required to reduce 6 molecules of CO2 to glucose. NADPH and ATP are essential energy carriers in the process of photosynthesis. Choice A is incorrect because it underestimates the required molecules of both NADPH and ATP. Choices C and D overestimate the number of molecules needed, making them incorrect answers.