Final answer:
The correct answer is option C, silicone-based hair products, which can build up on the hair and make it look dull, limp, and greasy. It is important to properly cleanse the hair after using these products.
Step-by-step explanation:
The correct answer is option C, silicone-based hair products. These products contain silicone, which can build up on the hair over time. This build-up can make the hair look dull, limp, and greasy. Additionally, it can prevent other hair care products, such as conditioner, from properly penetrating the hair shaft.
For example, using a silicone-based hair serum every day without thoroughly washing it out can lead to product build-up and damage the hair. It is important to properly cleanse the hair, especially if silicone-based products are being used.
On the other hand, options A (gel), B (hairspray), and D (natural oils) do not typically cause significant build-up on the hair when used in moderation.