Correct Answer: B

Rationale: The general formula for an alkene is \(C_nH_{2n}\), indicating the presence of a double bond between carbon atoms.

Correct Answer: C

Rationale: When an object moves through a fluid, it experiences resistance due to the viscosity of the fluid. This resistance is known as the viscous force, which opposes the motion of the object. Gravitational force is the force of attraction between two objects with mass, tension force is the force transmitted through a string, and magnetic force is the force exerted by magnets. In the context of an object moving through a fluid, the force opposing its motion is the viscous force because it resists the relative motion of the object through the fluid.

Correct Answer: A

Rationale: Mass is a measure of the amount of matter in an object and remains constant regardless of its location in the universe. Weight, on the other hand, is the force of gravity acting on an object and can vary depending on the gravitational pull at different locations. Density and volume can also change based on the environment in which an object is placed, making mass the property that remains constant universally. Therefore, the correct answer is mass. Weight changes with the gravitational force of a particular location, density varies with mass and volume, and volume can change depending on the shape or size of the object.

Correct Answer: B

Rationale: Pernicious anemia is caused by a deficiency in vitamin B12 (cobalamin). Vitamin B12 is essential for the production of red blood cells and for the proper functioning of the nervous system. Pernicious anemia occurs when there is a lack of intrinsic factor, a protein produced in the stomach that is necessary for the absorption of vitamin B12 in the digestive system. Vitamin A, Vitamin D, and Vitamin E deficiencies do not lead to pernicious anemia. Vitamin A deficiency can cause night blindness and skin issues, Vitamin D deficiency can lead to rickets or osteomalacia, and Vitamin E deficiency can result in neurological problems and muscle weakness.

Correct Answer: B

Rationale: Laser light differs from typical light sources due to its monochromatic nature (single color) and coherence (synchronized waves). This means that laser light consists of a single wavelength and synchronized waves, unlike typical light sources that emit a range of wavelengths and are incoherent. The monochromatic nature of laser light allows it to be of a single color, while coherence ensures that the waves are synchronized. These unique properties of laser light make it valuable for a wide range of applications in fields such as medicine, industry, and research. Choices A, C, and D are incorrect because laser light's distinguishing features are not related to enhanced brightness, increased velocity, or limited visibility to the human eye. Instead, it is the monochromatic nature and coherence that set laser light apart from typical light sources.