Which of the following actions is permissible under Hawaii time-sharing laws?

Informing a purchaser about a seven-day right to cancel their contract is permissible under Hawaii time-sharing laws because it aligns with the state's regulations designed to protect consumers in time-sharing transactions. Hawaii law mandates that purchasers be made aware of their cancellation rights to ensure they are fully informed about their options after entering into a contract. This includes the important detail that they have the right to change their minds within a specified period, promoting fair practices within the time-share industry.

In contrast, the other actions listed violate consumer protection principles. Offering a prize without disclosing the requirement of attending a presentation misleads consumers about the terms and conditions, while failing to include necessary captions in promotional materials can lead to confusion or misinterpretation by the consumers. Additionally, offering a prize without disclosing its purpose can also be seen as deceptive, as consumers need to understand what they are getting into. Thus, option B stands out as the only choice that promotes transparency and consumer rights in line with Hawaii's time-sharing laws.