Question

At low latitudes, the only interruption to tropical rainforest climates results from

Answer 1

At low latitudes, the only interruption to tropical rainforest climates results from the high altitude.
Only the places that are on a very high altitude are interrupting the chain of rain forests in the low latitudes. There's a certain point to which this type of climate is sustainable, so anything above that line belongs into another climate type and the rain forests are interrupted by this places.