The recommended children's dosage of Keflex is 25 to 50 mg/kg/day in divided doses. The maximum daily safe dosage for a child weighing 42 lb is: Round to the nearest tenth.

(Number Only, do not enter mg, kg, or day with your answer)

The correct answer is Choice A.Choice A rationale:Vomiting is a common sign of digoxin toxicity. It occurs due to the drug's effects on the gastrointestinal system, which can lead to nausea and vomiting as the body attempts to expel the toxin. This symptom is particularly significant as it can indicate elevated digoxin levels that may require medical intervention.Choice B rationale:Tachycardia, or an increased heart rate, can occur with digoxin toxicity; however, it is more commonly associated with inadequate therapeutic levels rather than toxicity itself. Digoxin usually causes bradycardia (a slower heart rate) when at therapeutic levels, making tachycardia less indicative of toxicity.Choice C rationale:Bradypnea, or slow breathing, is not a typical sign of digoxin toxicity. While respiratory issues can arise from various conditions, they are not specifically linked to digoxin levels. Monitoring respiratory rate is essential in clinical settings but does not directly correlate with digoxin toxicity.Choice D rationale:Seizures are not a common sign of digoxin toxicity. While severe cases might lead to neurological symptoms due to electrolyte imbalances or other complications, seizures are not typically associated with digoxin overdose. Instead, they may suggest other underlying issues requiring evaluation.

The correct answer is choice C: Concrete operations stage.

Choice A rationale:

The preoperational stage, which occurs roughly between ages 2 and 7, is characterized by egocentrism, animism, and a lack of conservation. Children in this stage struggle with understanding that quantities can remain the same even if their appearance changes. For instance, they might think that pouring water from a tall glass into a short, wide glass somehow changes the amount of water. This stage does not demonstrate the mental understanding required for the examples given in the question.

Choice B rationale:

The intuitive thought stage, which typically spans from ages 4 to 7, is marked by increased symbolic thinking but still lacks the capacity for logical and systematic reasoning. Children in this stage might be able to count and perform basic arithmetic, but they struggle with more complex operations and understanding the underlying principles of mathematical operations. This stage is not where the ability to understand the given math operations is firmly established.

Choice C rationale:

The concrete operations stage, which encompasses ages 7 to 11, is characterized by the development of logical and systematic thinking. Children in this stage are capable of understanding basic mathematical principles and operations, such as conservation of quantity and simple arithmetic. They can mentally manipulate numbers and understand that reversing an operation will yield the original quantity. Therefore, this stage is when the ability to understand that 1 + 3 = 4 and 4 - 3 = 1 occurs.

Choice D rationale:

The formal operations stage, typically beginning around age 11, is characterized by abstract and hypothetical thinking. This is when adolescents and adults can engage in complex reasoning and consider multiple possibilities and outcomes. The given math operations are not the focus of this stage; rather, it pertains to more advanced cognitive abilities like hypothetical problem-solving and deductive reasoning.