B and C are correct. A and D are wrong.
In questions, you invert the order of subject and verb (if there is an auxiliary verb like do, be, have, modals, you invert the auxiliary verb, not the main verb). Verb then subject
e.g. Do you have some time? Have you any time? Can I help you?
.
In statements, the order is usually subject then verb.
e.g. I have time. I can help you.
The confusion in your examples arises from the fact that question words such as "how", "why" can also be used in statements.
e.g.I know how to help you. I don't know where he is.