This is evidence that South America and Africa were once joined. The rare rock in question is unlikely to exist on both coasts if the continents weren’t joined at one point. And rocks last long enough to have been around back when the landmass broke apart.

These continents drifted away from each other in "prehistoric" times, long before humans existed. Genetic similarities must therefore have different explanations, such as migration, or just coincidence.

We don’t have any information connecting continental drift to climate. It’s very possible that western Africa and eastern South America have similar climates to each other for other reasons (e.g. being at the same latitude).

As in (B), continental drift happened long before humans were around. Any linguistic similarities between groups on different continents can't be related to continental drift.

First, we don't know if this resemblance indicates a relationship between these plants, or if it's just coincidental. Even if it's not a coincidence, the plants could have easily been carried across the ocean by humans or natural forces.