1. Pseudostratified columnar epithelium

A. Skeletal muscle
B. Bony skeleton
C. External ears
D. Bloodstream

Correct answer: C

Rationale: The correct answer is C: External ears. Pseudostratified columnar epithelium is a type of epithelial tissue found in the respiratory tract, where it appears to be stratified but all cells are anchored to the basement membrane. The external ears are lined with pseudostratified columnar epithelium to help protect and support the structures of the ear canal. Skeletal muscle (A) is a type of muscle tissue, bony skeleton (B) refers to bones, and bloodstream (D) is a system for blood circulation, which are not related to pseudostratified columnar epithelium.

2. When an atom gains or loses electrons, it becomes a(n):

A. Molecule
B. Isotope
C. Ion
D. Compound

Correct answer: C

Rationale: Gaining or losing electrons alters the atom's electron count and charge, creating a positively or negatively charged ion.

3. The final sentence highlights the need for

A. Public funding for scientific research and development of climate-friendly technologies.
B. Individual lifestyle changes and responsible consumption habits to reduce carbon footprints.
C. International partnerships and collaborative efforts to implement effective climate action plans.
D. Educational campaigns raising awareness about the urgency of addressing climate change.

Correct answer: C

Rationale: The emphasis on "international cooperation," "robust scientific research," and "adapting" suggests a focus on collaborative and multi-faceted solutions, aligning with C.

4. During exercise, heart rate increases to deliver more oxygen to the body's tissues. What other cardiovascular response also increases?

A. Blood pressure decreases
B. Blood vessel diameter narrows
C. Blood flow to muscles increases
D. Blood viscosity thickens

Correct answer: A

Rationale: The correct answer is A: 'Blood pressure decreases.' When the heart rate increases during exercise to deliver more oxygen to the body's tissues, the blood pressure also tends to decrease. This is due to the enhanced efficiency of the heart in pumping blood, resulting in a lower pressure exerted on the blood vessel walls. In contrast, options B and D are incorrect as blood vessel diameter typically widens (dilates) during exercise to facilitate increased blood flow, and blood viscosity does not usually thicken during exercise. Option C is a distractor as blood flow to muscles indeed increases during exercise to meet the higher demand for oxygen and nutrients.

5. When magnesium metal reacts with hydrochloric acid, hydrogen gas is produced. What evidence suggests a chemical reaction is occurring?

A. A change in color
B. The formation of a gas
C. Dissolving in a liquid
D. No change in temperature

Correct answer: B

Rationale: The correct answer is B: 'The formation of a gas.' When magnesium metal reacts with hydrochloric acid, hydrogen gas is produced as one of the products. The formation of a gas is a clear indicator of a chemical reaction taking place. This is known as a gas evolution reaction, where a gas is produced as a result of a chemical reaction. The other options do not specifically indicate a chemical reaction. A change in color or dissolving in a liquid could occur in physical changes as well, and no change in temperature does not necessarily rule out a chemical reaction as some reactions are endothermic or exothermic.

6. What is the name of the radioactive isotope commonly used in medical imaging techniques like PET scans?

A. Uranium-235
B. Plutonium-239
C. Potassium-40
D. Fluorine-18

Correct answer: D

Rationale: Fluorine-18 is the radioactive isotope commonly used in medical imaging techniques like PET scans. It is often used in the form of fluorodeoxyglucose (FDG) to detect areas of increased metabolic activity in the body, such as in cancer cells. Uranium-235 and Plutonium-239 are not typically used in medical imaging, and Potassium-40 is a naturally occurring radioactive isotope found in the human body but is not commonly used in medical imaging techniques.