1. Which of the following is NOT a symptom of asthma, a chronic respiratory condition?

A. Wheezing
B. Difficulty breathing
C. Chest tightness
D. Fever

Correct answer: D

Rationale: The correct answer is D: "Fever." Fever is not a symptom commonly associated with asthma. Asthma symptoms typically include wheezing (A), difficulty breathing (B), and chest tightness (C). Wheezing is a high-pitched whistling sound that occurs during breathing, while difficulty breathing refers to the feeling of not getting enough air. Chest tightness is a common sensation of pressure or constriction in the chest. Fever is not a typical symptom of asthma but may occur in other respiratory conditions or infections. Therefore, fever is the correct answer as it does not align with the typical symptom profile of asthma.

2. What is the function of the pericardium, the sac surrounding the heart?

A. o generate electrical impulses for heart contraction
B. To transport blood throughout the body
C. To provide lubrication for heart movement
D. To protect the heart and anchor it in place

Correct answer: D

Rationale: The pericardium, the sac surrounding the heart, serves primarily to protect the heart and anchor it in place. It acts as a protective barrier against external infections or damage and helps to maintain the heart's position within the chest cavity. Additionally, the pericardium also provides some degree of shock absorption to minimize physical trauma to the heart. While the heart's electrical impulses for contraction originate from within the heart itself and are not generated by the pericardium, it does not play a role in directly generating these impulses. Therefore, option D, 'To protect the heart and anchor it in place,' is the correct function of the pericardium.

3. What is the difference between a pure substance and a mixture?

A. Pure substances have fixed composition, mixtures don't.
B. Mixtures have fixed composition, pure substances don't
C. Pure substances are always solids, mixtures can be any state
D. Pure substances are always elements, mixtures are always compounds

Correct answer: A

Rationale: Rationale: - Pure substances have a definite and constant composition, meaning they are made up of only one type of atom or molecule. This composition does not vary. - Mixtures, on the other hand, are composed of two or more substances physically combined. The components of a mixture can be present in varying proportions, leading to a variable composition. - Option A correctly distinguishes between pure substances and mixtures based on the fixed composition of pure substances and the variable composition of mixtures.

4. What is the main function of valence electrons in chemical bonding?

A. They are responsible for holding the nucleus together.
B. They are involved in forming bonds with other atoms.
C. They determine the element's physical properties.
D. They play no role in chemical reactions.

Correct answer: B

Rationale: They are involved in forming bonds with other atoms. Valence electrons occupy the outermost energy level and are readily involved in attracting other atoms through sharing or transferring electrons, forming chemical bonds.

5. Negative feedback mechanisms are crucial in the endocrine system to:

A. Increase hormone production continuously
B. Maintain hormone levels within a specific range
C. Cause a constant release of hormones
D. Disrupt communication between glands

Correct answer: B

Rationale: The correct answer is B: 'Maintain hormone levels within a specific range.' Negative feedback mechanisms in the endocrine system are essential for regulating hormone levels. These mechanisms work to counteract any deviations from the set point, ensuring that hormone levels remain balanced and within the optimal range for proper physiological function. Continuous hormone production (A) or constant release of hormones (C) would lead to imbalances and potential harm to the body. Disrupting communication between glands (D) would hinder the coordination necessary for maintaining homeostasis. Therefore, option B is the best choice as it highlights the critical role of negative feedback in keeping hormone levels stable and regulated.