Final answer:
The correct statement indicating an understanding of post-radiation therapy skin care is avoiding the application of lotions or creams to the treated area to prevent interference with treatment.
Step-by-step explanation:
The question concerns a client who is undergoing external radiation therapy for cancer. The client's understanding of skin care during treatment can be discerned by their statement. The correct statement that indicates an understanding would be: "I will avoid applying any lotion or cream to the treated skin." For radiation therapy, it's essential to maintain the integrity of the radiation marks and to prevent any substances from interfering with the treatment area. Hot water may irritate the skin, direct sunlight can exacerbate skin sensitivity and damage, and tight clothing can further irritate the skin. Therefore, these options are not recommended for someone receiving radiation therapy.