Too strong. Although the author does mention that herds can help a pronghorn “watch for predators” and “diminish the chances of any particular animal being attacked,” this doesn’t support the claim that predators “do not attack” grazing animals in herds. They may still attack herds — it’s just that on average, an individual member of the herd decreases its chances of being among the animals that are caught and eaten.

Not supported, because the author never suggests there are any conditions or requirements on when the pronghorns will graze in herds. Although we only get mention of benefits related to predators, this doesn’t imply that pronghorns only herd when predators are nearby. Perhaps pronghorns generally herd, regardless of whether predators are nearby, so that they can benefit if a predator comes along.

Not supported, because although we know that many grazing animals herd, this doesn’t imply that only grazing animals herd. Maybe non-grazing animals herd and also get benefits from herding.

Too strong. Although the author does indicate that female pronghorns “choose mates based on [speed and endurance],” this doesn’t imply that they mate “only” with the fastest male pronghorn. Maybe the top few pronghorns mate with females, or the top 10%. Also, speed is only one aspect of the athletic abilities mentioned.

Supported. We’re told that pronghorns have “nothing to fear from present-day carnivores” (because pronghorns are much faster than them). So, pronghorns’ herding doesn’t currently protect them from predators. The present-day predators wouldn’t be able to catch the pronghorns regardless of their herding. That’s why the passage supports the claim that if pronghorns didn’t herd, they wouldn’t face a lot more danger from present-day carnivores.