Given the task definition and input, reply with output. 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".

[header] How to do yoga with a bad back [title] Talk to your healthcare provider. [step] Your back is a very tricky area to exercise and strengthen. If not done carefully, you can injure yourself more. <sep> (A) By talking to your healthcare provider, you can ask for help setting up some exercises. [substeps] Ask a volunteer or someone who is an experienced yoga instructor who has trained or worked with patients with a bad back. (B) If you are exercising your back too much, you could be at risk of injuring it further. Talk to your general practitioner or a therapist before stretching. (C) So before you begin a yoga routine, make sure to get clearance from your healthcare provider. [substeps] If you have a bad back, talk to your healthcare provider about what types of exercises can help relieve pain, tightness and help you strengthen those essential muscles. (D) Not a good idea when you are facing an acute back injury and it makes it difficult for you to exercise. Consider switching to a physical trainer or doing yoga alone.
C