Two or more keywords or phrases. As many keywords as possible. The same keywords on each page. A is usually the best choice, but B is perfectly acceptable. C is not a good idea because then no keyword or phrase stands out.
D misses the point.
Pages that focus on 1 - 3 keywords or phrases will always rank higher for that keyword than a page that has not been optimized. The most important keyword or phrase on each page is . . . Featured in headlines and in page content. Again, A is by far the best choice. There is a catch-22 in this ranking business.