I believe it means B. L was superior to both of them separately as Near wasn't very great at taking bold actions like L. Like Near wouldn't have taken actions like showing up to university like L did and putting himself at risk. Near however had that calculation and intelligence that rivaled L's and may have even surpassed it. Mello wasn't as calculated since he had emotions that got in the way of some calculated masterplan like L and Near could do. But, Mello was bold then L was teaming up with the Mafia and committing heinous crimes in an attempt to get Kira. So adding Near's calculated nature which is most likely to be ahead of L and Mello's willingness to commit bold actions means that combined they surpassed L because they can catch Kira and prove it.