I think I can see why not so many people chose the option "intelligence varies considerably across races". Of course, different races have different characteristics, which could be the result of an inextricable mixture of genetic factors and social/cultural factors (although we're thinking of genetics here). For example Maciamo pointed out the various sports at which certain races excel. But, differences in racial characteristics do not necessarily translate to "more" or "less" intelligent. So, you could say that, genetically, certain races are more likely to contain a much higher proportion of people whose brains work in a certain way (as suggested by the examples of the types of music), but, you can't say that makes these people - on average - any more or less intelligent than those of another race. It's just... difference.