Correct Answer: A

Rationale: The correct answer is A: Nucleic acids. DNA and RNA are both types of nucleic acids, which are fundamental biological molecules responsible for storing and transmitting genetic information. Choice B, Proteins, are not subunits of DNA and RNA but are composed of amino acids. Carbohydrates, choice C, are another type of biological molecule involved in energy storage and structural support, not subunits of DNA and RNA. Lipids, choice D, are a diverse group of molecules that include fats, oils, and steroids, but they are not subunits of DNA and RNA.

Correct Answer: A

Rationale: The correct answer is A: To produce amino acids. During the translation stage of protein synthesis, the mRNA is decoded to assemble a specific sequence of amino acids. These amino acids then fold into a functional protein. Choices B, C, and D are incorrect because the translation stage specifically deals with the production of amino acids, not nucleotides, fatty acids, or nucleic acids.

Correct Answer: C

Rationale: The correct answer is 0%. If one parent carries the recessive gene for a cleft chin while the other parent does not, none of the offspring will express the recessive phenotype. This is because in order for a child to have a cleft chin, they would need to inherit the recessive gene from both parents. Therefore, although the offspring could be carriers of the gene, none are predicted to have a cleft chin. Choices A, B, and D are incorrect because the presence of the recessive gene in one parent and its absence in the other would not result in any offspring showing the cleft chin trait.

Correct Answer: B

Rationale: Asexual reproduction is a type of reproduction where a single parent cell divides to produce genetically identical offspring. The correct answer is 'B: A single cell' because asexual reproduction does not involve the fusion of two cells. Choice A ('Two identical cells') is incorrect because asexual reproduction does not involve two cells. Choice C ('Two cells') is incorrect because asexual reproduction typically involves only one parent cell. Choice D ('Four daughter cells') is incorrect because asexual reproduction does not necessarily involve the production of four daughter cells.

Correct Answer: C

Rationale: The correct answer is C, the citric acid cycle (the Krebs cycle). This cycle generates NADH and FADH2, which play a crucial role in providing electrons to the electron transport chain during cellular respiration. Choice A, the electron transport chain itself, is where NADH and FADH2 donate their electrons, not where they are produced. Choice B, glycolysis, produces NADH but not FADH2. Choice D, 'None of these,' is incorrect as the citric acid cycle specifically produces NADH and FADH2.