Answer:
The words in the passage which show that is has a problem and solution structure are:
A. This is a problem.
Explanation:
As the name suggests, a problem and solution structure is used to present a problem, issue, or even a dilemma and then the possible solutions that can be or have already been attempted. Some authors will describe the problem without actually using the word "problem". Others will choose to make it as clear and direct as possible, which is the case here. The author of the excerpt wants to make it crystal clear that the killing of crocodiles is an issue that needs to be addressed, so he uses the words "this is a problem". He then explains why that is a problem and, even though we only have a passage here, we can safely assume he will offer option for solutions.