Correct Answer: D

Rationale: The correct answer is Helium (He). Helium has an atomic number of 2, meaning it has 2 protons. It also has 2 neutrons, which gives it a total mass number of 4. Therefore, Helium is an example of an element with an equal number of protons and neutrons. Choice A (Carbon) has 6 protons and usually has more neutrons than protons. Choice B (Oxygen) has 8 protons and 8 neutrons, so the numbers are not equal. Choice C (Lithium) has 3 protons and usually has more neutrons than protons, so it does not fit the criteria of having the same number of protons and neutrons.

Correct Answer: B

Rationale: Testosterone is a hormone primarily produced in the testes of males and is responsible for the development of male reproductive tissues, including the testes and prostate. Its primary function is the production and maturation of sperm cells, as well as the development of secondary sexual characteristics in males. Choice A, 'Egg production,' is incorrect as testosterone is not involved in the production of eggs. Choice C, 'Regulation of the menstrual cycle,' is incorrect because testosterone is not responsible for regulating the menstrual cycle, which is primarily governed by female hormones. Choice D, 'Milk production,' is incorrect as testosterone does not play a role in milk production, which is associated with other hormones like prolactin in females.

Correct Answer: B

Rationale: Phosphorus is the correct answer. It is used in fertilizers due to its essential role in plant cell division and growth. Phosphorus is a key component of nucleic acids, such as DNA and RNA, which are essential for cell division and growth in plants. Potassium (Choice A) is important for overall plant health and functions like enzyme activation, but it is not specifically known for its role in cell division and growth. Calcium (Choice C) is crucial for cell wall structure and stability but not primarily for cell division. Magnesium (Choice D) is essential for chlorophyll production and photosynthesis, but it is not directly linked to plant cell division and growth.

Correct Answer: B

Rationale: Work is directly proportional to displacement. In physics, work is defined as the product of the force applied to an object and the displacement of the object in the direction of the force. Therefore, work is directly proportional to displacement. Choice A is incorrect because work is dependent on both force and displacement. Choice C is incorrect because work is not inversely proportional to displacement; it is directly proportional. Choice D is incorrect because work is indeed related to displacement, as described in the definition of work in physics.

Correct Answer: C

Rationale: The correct answer is C, Gliding joint. Gliding joints allow for side-to-side bending movements. These joints are found between the small bones of the wrist and ankle, allowing for flexibility and movement in multiple directions. Hinge joints (A) enable movement in one plane, akin to a door hinge. Ball-and-socket joints (B) allow for a wide range of motion across multiple directions. Saddle joints (D) facilitate movement in two planes.