Scoliosis is a condition characterized by abnormal lateral curvature of the spine. Which part of the spine is most commonly affected?

Correct Answer: B

Rationale: Scoliosis most commonly affects the thoracic spine, which is the upper back region. While scoliosis can potentially affect any part of the spine, the thoracic spine is the most frequently involved area. This region is more commonly affected due to the natural structural curves of the spine and the biomechanics of the thoracic area. The cervical spine (neck) and lumbar spine (lower back) can also be affected by scoliosis, but the thoracic spine is the primary area of involvement in most cases. Therefore, the correct answer is B, as it is the part of the spine most commonly affected by scoliosis.

Correct Answer: C

Rationale: The second harmonic (first overtone) is twice the frequency of the fundamental frequency. Therefore, the frequency of the second harmonic is 440 Hz * 2 = 880 Hz. The second harmonic has a frequency that is one octave higher than the fundamental frequency, representing the first overtone of the vibrating string. Choice A (220 Hz) is incorrect as it represents half the fundamental frequency and is the second harmonic, not the first overtone. Choice B (440 Hz) is the fundamental frequency itself. Choice D (1760 Hz) is the frequency of the fourth harmonic, not the second harmonic.

Correct Answer: C

Rationale: When a light ray travels from air (lower refractive index) to water (higher refractive index), its speed decreases due to the change in the medium. This is because light travels slower in denser mediums. As the light ray enters the denser medium, water in this case, it bends towards the normal (the line perpendicular to the surface of the water). This phenomenon is known as refraction. Choice A is incorrect as the speed of light decreases when entering a denser medium. Choice B is incorrect as the direction bends towards the normal, not away from it. Choice D is incorrect as the speed and direction of the light ray do change when moving from air to water.

Correct Answer: B

Rationale: The main difference between a nuclear reactor and a nuclear bomb is that reactors have controlled chain reactions, while bombs have uncontrolled chain reactions. Nuclear reactors are designed to sustain a controlled nuclear reaction to generate electricity. In contrast, nuclear bombs are designed to release a massive amount of energy in an uncontrolled chain reaction, resulting in an explosion. Choice A is incorrect because both reactors and bombs can use enriched uranium. Choice C is incorrect as nuclear reactors also generate electricity, not just bombs. Choice D is incorrect because both reactors and bombs may or may not use moderators, but the key distinction lies in the control of the chain reaction.

Correct Answer: D

Rationale: Blood type O is considered the universal donor because individuals with type O blood can donate red blood cells to individuals with any ABO blood type (A, B, AB, or O) without causing an adverse reaction. Type O blood lacks A or B antigens on the surface of red blood cells, minimizing the risk of an immune response when transfused into individuals with different blood types. Therefore, type O blood is in high demand for blood transfusions in emergency situations when the recipient's blood type is unknown or when there is a shortage of specific blood types. Choices A, B, and AB are not considered universal donors. Individuals with blood types A, B, or AB can only donate to individuals with compatible blood types to avoid adverse reactions since they have A and/or B antigens on the surface of their red blood cells, making them incompatible with all blood types.