Final answer:
The nurse should monitor a child taking methylphenidate for elevated blood pressure, which is a possible adverse effect of this stimulant medication used to treat ADHD.
Step-by-step explanation:
Methylphenidate is a stimulant medication commonly used to treat Attention-Deficit/Hyperactivity Disorder (ADHD) and narcolepsy. It functions by increasing levels of certain neurotransmitters in the brain, which helps increase attention and focus, but it can also have adverse effects. While increased attention is a therapeutic effect of methylphenidate, it is not considered an adverse effect. The nurse should monitor for elevated blood pressure, as it is a potential adverse effect of stimulant medications like methylphenidate. Other possible side effects include decreased appetite and insomnia, but not decreased energy levels which would be contrary to the drug's effects. Therefore, the correct answer is: b. Elevated blood pressure.