ATI TEAS Practice Science Test

Correct Answer: D

Rationale: The correct answer is D: Oxygen. 1. Oxygen has 8 electrons in total, with 2 in the first shell and 6 in the second shell, following the 2-8-8 electron configuration rule. 2. Beryllium has 4 electrons with 2 in the first shell and 2 in the second shell. 3. Carbon has 6 electrons with 2 in the first shell and 4 in the second shell. 4. Helium has 2 electrons, filling the first shell. Therefore, Oxygen is the only element among the choices that fits the description of having 2 electrons in the first shell and 6 electrons in the second shell.

Correct Answer: D

Rationale: The correct answer is D: Melanocyte-stimulating hormone. Melanocyte-stimulating hormone stimulates the melanocytes in the skin to produce melanin, the pigment responsible for skin color. This hormone darkens the skin by increasing melanin production. A: Follicle-stimulating hormone is involved in reproductive functions, not skin color changes. B: Growth-stimulating hormone primarily affects growth and development, not skin color. C: Thyroid-stimulating hormone regulates thyroid function, not skin color.

Correct Answer: C

Rationale: The independent variable is the factor that is intentionally changed by the researcher. In this study, the type of road salt used is the independent variable because it is what the researcher is manipulating to observe its effect on the deicing time. The researcher can control and vary the type of road salt to measure its impact on the deicing process. The other choices are not the independent variable because: A (Deicing time period) is the dependent variable, B (Road used for deicing) is not something that the researcher is intentionally changing, and D (Amount of road salt used) is a controlled variable that can be adjusted but not the main factor being manipulated.

Correct Answer: C

Rationale: The correct answer is C because fetal waste is passed down the umbilical cord to the mother's circulatory system. The developing fetus eliminates metabolic wastes primarily through the placenta, which acts as a filter between the fetal and maternal circulatory systems. Metabolic wastes from the fetus, such as carbon dioxide and urea, diffuse through the placenta into the mother's bloodstream for elimination by her kidneys and lungs. This process ensures that the fetus's metabolic wastes are effectively removed without burdening its own developing organs. Choices A, B, and D are incorrect: A: The developing fetus does produce metabolic wastes, which need to be eliminated for proper development. B: Fetal waste does not pass through the mother's digestive system; it would be harmful to both the mother and fetus. D: Fetal waste does not exit the mother's body via the vagina; this is not a mechanism for waste elimination in utero.

Correct Answer: D

Rationale: The correct answer is D because it specifically refers to the process of selective permeability by stating that sodium ions must travel through ion channels to enter the cell. This demonstrates that the cell membrane allows certain substances to pass through while blocking others. Receptors on the cell's surface (A) and cell communication (B) are related to cell function but do not directly confirm selective permeability. Environmental changes affecting cell size (C) are more about cell response than membrane permeability. In summary, choice D is correct because it directly addresses the concept of selective permeability, while the other choices do not provide direct evidence of this property.