ati teas 7 science

Correct Answer: B

Rationale: The correct answer is B: Atom. An atom is the smallest unit of matter that retains the properties of an element. Atoms are made up of protons, neutrons, and electrons. A molecule (A) consists of two or more atoms bonded together. A compound (C) is a substance composed of two or more different elements chemically bonded. An element (D) is a pure substance made up of only one type of atom. Therefore, the smallest unit of matter is the atom.

Correct Answer: C

Rationale: Step 1: Amphiprotic substances can donate and accept protons, making them capable of acting as both acids and bases. Step 2: When amphiprotic substances react, they can donate or accept protons depending on the reaction conditions. Step 3: This ability allows them to exhibit properties of both acids and bases. Step 4: Therefore, Choice C is correct as it accurately describes the nature of amphiprotic substances. Summary: A: Incorrect - Amphiprotic substances can react with both acids and bases, not just acids. B: Incorrect - Amphiprotic substances can react with both acids and bases, not just bases. D: Incorrect - Amphiprotic substances are not inert; they actively participate in chemical reactions by donating and accepting protons.

Correct Answer: B

Rationale: Platelets are responsible for blood clotting, which is crucial for preventing excessive bleeding when a blood vessel is injured. They adhere to the site of injury and form a plug to stop bleeding. This function is essential for maintaining hemostasis in the body. Platelets do not carry oxygen like red blood cells (Choice A), fight infection like white blood cells (Choice C), or transport nutrients like plasma (Choice D).

Correct Answer: C

Rationale: The correct answer is C: Buffering system. The body maintains a relatively constant blood pH level through the buffering system, which involves the action of bicarbonate ions, carbonic acid, and other buffering molecules that help regulate pH by neutralizing excess acids or bases. This system acts quickly to prevent drastic changes in blood pH when there are fluctuations in blood carbon dioxide concentration. Cellular respiration (A) generates carbon dioxide, gas exchange (B) involves the exchange of gases in the lungs, and deoxygenation (D) refers to the loss of oxygen by the blood, but these processes are not primarily responsible for maintaining blood pH stability.

Correct Answer: D

Rationale: The correct answer is D because all the options are valid obstacles to achieving controlled nuclear fusion on Earth. Lack of suitable materials (A) is crucial due to extreme conditions, limited fusion fuels (B) can hinder sustained reactions, and containing plasma (C) is challenging to prevent energy loss. Therefore, all factors must be addressed for successful fusion energy production.