1. A hypothesis should be:

A. A definitive statement of fact based on existing knowledge.
B. A testable prediction based on observations and reasoning.
C. A broad question without any specific direction or focus.
D. A personal belief or opinion not requiring further investigation.

Correct answer: B

Rationale: Hypotheses guide scientific exploration by providing a framework for testing potential explanations.

2. Which hormone is responsible for regulating sleep-wake cycles and is influenced by light exposure?

A. Melatonin
B. Cortisol
C. Estrogen
D. Glucagon

Correct answer: A

Rationale: The correct answer is A: Melatonin. Melatonin is a hormone produced by the pineal gland in the brain and plays a crucial role in regulating the sleep-wake cycle, also known as the circadian rhythm. Melatonin levels typically rise in the evening in response to darkness and help signal to the body that it's time to sleep. Exposure to light, especially blue light, can inhibit the production of melatonin, making us more alert and awake. Cortisol (option B) is a stress hormone that helps regulate metabolism and immune response. Estrogen (option C) is a female sex hormone, and glucagon (option D) is a hormone that increases blood sugar levels. Therefore, the hormone responsible for regulating sleep-wake cycles and influenced by light exposure is melatonin.

3. Which of the following is a weak acid commonly found in citrus fruits?

A. Sulfuric acid (Hâ‚‚SOâ‚„)
B. Hydrochloric acid (HCl)
C. Citric acid
D. Nitric acid (HNOâ‚ƒ)

Correct answer: c

Rationale: Citric acid is a weak acid commonly found in citrus fruits. The other choices are strong acids.

4. What is the scientific term for the monthly cycle in females that prepares the body for potential pregnancy?

A. Ovulation cycle
B. Menstrual cycle
C. Implantation cycle
D. Gestation cycle

Correct answer: B

Rationale: The correct answer is B: 'Menstrual cycle.' The menstrual cycle is the scientific term for the monthly process in females that prepares the body for potential pregnancy. During this cycle, the lining of the uterus thickens to prepare for a fertilized egg, and if no fertilization occurs, the uterus sheds this lining in the form of menstrual bleeding. Ovulation cycle refers specifically to the release of an egg from the ovary, implantation cycle is the process of a fertilized egg attaching to the uterine wall, and gestation cycle is the period of pregnancy from conception to birth. Therefore, the menstrual cycle is the most appropriate term for the monthly process described in the question.

5. What is the difference between isometric and isotonic muscle contractions?

A. Isometric involves movement, while isotonic does not.
B. Isotonic involves shortening of muscle, while isometric maintains length.
C. Isometric uses more energy, while isotonic uses less.
D. Isotonic involves smooth muscle, while isometric involves skeletal muscle.

Correct answer: B

Rationale: The correct answer is B: "Isotonic involves shortening of muscle, while isometric maintains length." Isometric contractions occur when the muscle generates force without changing its length, such as holding a weight in a fixed position. On the other hand, isotonic contractions involve the muscle changing length, either by shortening (concentric contraction) or lengthening (eccentric contraction) while generating force. Understanding this distinction is crucial for grasping the different types of muscle contractions and their effects on the body during exercise and movement.

6. What is the term for a genetic disorder caused by a mutation on the X chromosome?

A. Autosomal dominant disorder
B. Autosomal recessive disorder
C. Sex-linked recessive disorder
D. Sex-linked dominant disorder

Correct answer: C

Rationale: Rationale: - Autosomal dominant disorders (Option A) are caused by a mutation in one copy of a gene on one of the non-sex chromosomes (autosomes). These disorders do not specifically involve the X chromosome. - Autosomal recessive disorders (Option B) are caused by mutations in both copies of a gene on the autosomes. They are not directly related to mutations on the X chromosome. - Sex-linked dominant disorders (Option D) are rare and typically result in more severe symptoms in males because they only need one copy of the mutated gene on the X chromosome to express the disorder. This is not the term for a genetic disorder caused by a mutation on the X chromosome. - Sex-linked recessive disorders (Option C) are genetic disorders caused by mutations on the X chromosome. These disorders are more commonly seen in males because they have only one X chromosome, making them more susceptible to X-linked mutations. Females have two