In order to answer this question, I tried to think of all the couples I know reasonably well, rank order them in terms of the level of similarity of the two members, and then see whether more couples at the "similar" end or "dissimilar" end of the scale appear to have sustained a successful relationship over the long term.

This procedure made option B appear to be the clear favorite. Option C was almost nonexistent among the couples I considered. (Most of these couples were married, and people don't choose a marriage partner out of convenience.) Option A was common but was correlated with the less-successful couples.

These results are, of course, skewed by the sorts of people I tend to know. I'd be hesitant trying to apply these results to other countries, other socio-economic classes, etc.