When teaching a class about trisomy 21, the instructor would identify the cause of this disorder as:

Correct Answer: A

Rationale: The correct answer is A: nondisjunction. Trisomy 21, also known as Down syndrome, is caused by nondisjunction, which is an error in cell division leading to an extra copy of chromosome 21. This additional genetic material alters the course of development and causes the characteristics associated with Down syndrome. Choices B, C, and D are incorrect. X-linked recessive inheritance refers to genetic disorders carried on the X chromosome, genomic imprinting involves gene expression based on parental origin, and autosomal dominant inheritance relates to disorders caused by a dominant gene on one of the non-sex chromosomes. In the case of trisomy 21, the cause is specifically related to the error in chromosome division, making nondisjunction the most appropriate answer.

Correct Answer: B

Rationale: When parents of a toddler request to be present during a procedure, an individual assessment of the parents is crucial. This assessment helps healthcare professionals understand the parents' ability to cope with the situation, provide support to their child, and ensure a conducive environment for the procedure. Choice A is not as critical because the focus is on the parents' readiness rather than the specific procedure. Choice C, considering the toddler's desire, is important but not as crucial as assessing the parents. Choice D, anticipating the toddler's response to pain, is relevant but secondary to assessing the parents' readiness and support capabilities.

Correct Answer: B

Rationale: The correct answer is B: "Toddlers are learning to assert independence, and this behavior is expected at this age." At 18 months, toddlers are in the stage of developing autonomy and independence. They may exhibit behaviors like temper tantrums and defiance as they assert their independence and test limits. It is crucial for parents and caregivers to understand that these behaviors are typical for toddlers at this age. Choice A is incorrect because discipline should be age-appropriate and focus on positive reinforcement rather than preventing antisocial behaviors. Choice C is inappropriate as leaving a toddler alone in a crib after explaining unacceptable behavior is not a recommended approach and can lead to feelings of abandonment. Choice D is inaccurate as the described behavior is more related to asserting independence rather than the initiative stage of development.

Correct Answer: D

Rationale: Macaroni and cheese and Cheerios are appropriate choices for a 30-month-old toddler on a regular diet. These foods are easy to chew, digest, and are generally well-liked by toddlers. Option A, a hamburger with bun and grapes, may be difficult for a toddler to handle due to the size of the hamburger and grapes pose a choking hazard. Option B, chicken fingers and french fries, may be too greasy and processed for a toddler's developing digestive system. Option C, hot dog with bun and potato chips, is also not ideal as hot dogs can be a choking hazard and potato chips are high in salt and may not provide adequate nutrition.

Correct Answer: D

Rationale: The most crucial factor in the process of toilet training is the parents' willingness to consistently engage and work with their child. While parents' attitude and the child's desire to remain dry can influence the process, the key to successful toilet training lies in the parents' commitment and effort. The child's ability to sit still on the toilet is important but not as critical as the parents' active involvement and support in guiding and encouraging the child through the training process.