Correct Answer: A

Rationale: The correct answer is A: Ribosomes. Ribosomes are the organelles responsible for protein synthesis in the cell. They can be found either freely floating in the cytoplasm or attached to the endoplasmic reticulum. The Golgi apparatus (Choice B) is involved in processing and packaging proteins, not protein production. Mitochondria (Choice C) are responsible for energy production, not protein synthesis. Lysosomes (Choice D) are involved in digestion and waste removal, not protein production.

Correct Answer: C

Rationale: A) Epigenetic variation refers to changes in gene expression that do not involve alterations in the DNA sequence itself. These changes can be influenced by environmental factors. B) Phenotypic variation refers to differences in observable traits or characteristics of an organism, which can be influenced by both genetic and environmental factors. C) Genotypic variation is caused by changes in the DNA sequence, such as mutations or genetic recombination. These changes directly impact the genetic information carried by an organism. D) Behavioral variation refers to differences in behavior among individuals of the same species, which can be influenced by genetic, environmental, and experiential factors.

Correct Answer: C

Rationale: Osteoporosis is a condition characterized by a loss of bone density, leading to fragile bones and an increased risk of fractures. Osteoarthritis is a degenerative joint disease affecting cartilage, Rickets is caused by a deficiency in vitamin D leading to impaired bone development, and Scoliosis is an abnormal sideways curvature of the spine. Therefore, the correct answer is osteoporosis as it specifically pertains to decreased bone density and fracture risk, distinguishing it from the other conditions listed.

Correct Answer: C

Rationale: The Doppler effect is the perceived change in frequency of a wave due to relative motion between the source of the wave and the observer. This phenomenon is commonly observed with sound waves, where the pitch of a sound appears higher as the source moves towards the observer and lower as the source moves away. Option A is incorrect as the Doppler effect primarily applies to sound waves, not light waves. Option B is incorrect because the Doppler effect is not about the change in wave speed due to medium density but rather a change in perceived frequency. Option D is incorrect as it describes wave bending due to different mediums, which is not the primary concept behind the Doppler effect. Therefore, option C accurately describes the Doppler effect and its application to the shift in frequency of sound waves perceived by an observer.

Correct Answer: B

Rationale: Genetic markers are specific DNA sequences that can vary among individuals. In paternity testing, genetic markers are used to compare the DNA of the child with that of the alleged father. By analyzing the presence or absence of specific alleles (different forms of a gene) at these genetic markers, scientists can determine the likelihood of paternity. This method is more accurate and reliable than comparing blood types (choice C) or physical resemblance (choice D) as genetic markers provide a direct comparison of DNA sequences between individuals. Therefore, option B is the correct choice as it accurately describes the use of genetic markers in paternity testing.