Answer:
The sentence that uses a colon correclty is sentence B.
Step-by-step explanation:
Sentence B uses a colon correctly. A colon means that is to say or here's what I mean. In the sentence above, the colon has been used to introduce a series of items. These items include eating well, sleeping enough, drinking water, and doing exercise. What is more, you should not capitalize the first item after the colon (eat well).