The best description of hominid evolution over the last few million years, particularly in relation to brain size and overall intelligence, is:
A: brain size and intelligence have increased.
This reflects the general trend observed in the evolution of hominids, particularly among the genus Homo, where there has been an increase in brain size that correlates with advancements in cognitive abilities and tool use. However, it's important to note that intelligence is a complex trait and cannot be solely measured by brain size. But overall, the trend in hominid evolution shows an increase in brain size alongside increases in various forms of cognitive abilities.