Use of the ampersand & and

When is it appropriate to use an ampersand “&” instead of the word “and”?

[A]   Ampersands should be used anywhere the letter pair “et” exist. &ymology instead of etymology.

[B]   Ampersands should be avoided unless they are part of a company name or a commonly used abbreviation (R&D)

[C]   The ampersand should never be used. It’s punctuation and doesn’t belong in most contexts.

[D]   The decision to use “and” or “&” is a matter of personal habit.