Choice B rationale:

The nurse accurately informs the client that they are contagious for about a week after the rash appears. The period of contagiousness starts a few days before the rash appears and continues until approximately 4 days after the rash has emerged. Measles is highly contagious, and transmission occurs through respiratory droplets from coughing or sneezing.

Choice A rationale:

This statement is incorrect. The client is contagious a few days before the rash appears and not only from the onset of the rash until two days afterward.

Choice C rationale:

This statement is incorrect. The client is contagious during the prodrome stage, which is before the appearance of the rash, as well as during the exanthematous stage when the rash is present.

Choice D rationale:

This statement is incorrect. The fever subsides during the prodrome stage, but the client remains contagious during the early part of the exanthematous stage when the rash is present.