Correct Answer - Option 1 : Only (A)
Option 1, Only A.
The passage mentions that salamander feed on leaf-eating insects which in their turn convert carbon present in the leaves into methane and if there are not many insects left then the leaves are converted into humus instead.
From what has been supplied it can be deduced that if the number of salamanders increase then they will feed on more and more insects and the fallen leaves will be left to decay and transform into humus. Therefore, statement A can be inferred.
But from what has been supplied we cannot infer that all the insects only eat leaves and nothing else. Therefore, statement B cannot be inferred.
Also from what is given, it cannot be deduced that soil rich in humus is good or bad. Therefore statement C cannot be inferred.
Hence,option 1 is correct.