Detailed Instructions: In this task, you are given a context and four options. Each option is a suggested ending for the context. You should read the context and pick the best ending for the context. Please answer with "A", "B", "C", and "D".
Problem:[header] How to clean your retainer [title] Rinse off the retainer with warm or cold (not hot) water. [title] Place the retainer in a shallow cup, big enough to fully hold it. [title] Pour vinegar into the cup until the retainer is fully submerged. <sep> (A) [title] Squirt some removable metal adhesive, such as acrylic or polyurethane, onto the retainer. [title] Secure the retainer with some foam sealants, if desired. (B) [title] Let it sit for 2 to 5 minutes. [step] Longer is not necessary, as the vinegar could begin to degrade the plastic. (C) [step] Alternatively, you can warm the retainer instead. [title] Strain out excess water using a strainer or a fine strainer. (D) [step] Tea tree oil and camphor can also be used. [title] Place the retainer in the bag.
Solution:
B