Ritodrine is a drug indicated for suppressing uterine contractions in premature labor. The drug also causes bronchodilation. It has no vasoconstrictor effects, nor any effects on the size of the pupil of the eye. Which of the following is the most likely classification of this drug?

Correct Answer: C

Rationale: The correct answer is C: β-adrenergic agonist. Ritodrine is indicated for suppressing uterine contractions, which is a typical effect of β-adrenergic agonists. Bronchodilation is also a known effect of β-adrenergic agonists. Since the drug has no vasoconstrictor effects and does not affect the size of the pupil of the eye, it is unlikely to be an α-adrenergic agonist or an antimuscarinic drug. Additionally, the fact that ritodrine causes bronchodilation further supports its classification as a β-adrenergic agonist.

Correct Answer: C

Rationale: The correct answer is C because in a fuel cell, the chemical product is water (H2O) produced from the reaction of hydrogen and oxygen, and the energy used to power the vehicles is electrical energy generated from the electrochemical reaction in the fuel cell. Choice A (hydrogen, electrical) is incorrect because hydrogen is the input fuel, not the output product. Choice B (hydrogen, thermal) is incorrect because thermal energy is not the primary form of energy produced in a fuel cell. Choice D (water, thermal) is incorrect because while water is the product, the energy produced is electrical, not thermal.

Correct Answer: D

Rationale: The correct answer is D: 600 cm/s. The speed of a wave is determined by the formula speed = frequency x wavelength. Given that the frequency and wavelength are constant, the only way to increase the speed is to increase the frequency or the wavelength. Since both frequency and wavelength are fixed, the speed can only be increased by increasing both. Choice D, 600 cm/s, is double the speed of choice C, 300 cm/s, which indicates that both frequency and wavelength have been doubled, leading to the correct answer. Choices A and B are too low to be correct, as they are not consistent with the principles of wave speed calculation.

Correct Answer: B

Rationale: The correct answer is B: steroid hormones. Steroid hormones are known to regulate gene expression by binding to specific receptors and influencing transcription processes. They can directly affect the transcription of new messenger RNA in the cell. Pancreatic hormones (A), catecholamines (C), and pituitary gland hormones (D) are not directly involved in the transcription of new messenger RNA. Pancreatic hormones primarily regulate blood sugar levels, catecholamines are involved in the fight-or-flight response, and pituitary gland hormones regulate various functions such as growth, reproduction, and metabolism.

Correct Answer: B

Rationale: Excess growth hormone suppresses cancer by promoting healthy cell growth and inhibiting apoptosis. Diabetes can result from growth hormone excess due to insulin resistance. Giantism in children and acromegaly in adults are both caused by excess growth hormone stimulating excessive skeletal and soft tissue growth. Therefore, the correct answer is B because excess growth hormone does not suppress cancer; it actually promotes cell growth and proliferation.