The correct answer is C. Given advance information.
Sobhraj could be easily arrested because the police were tipped off in advance. This means that someone gave the police information about Sobhraj’s whereabouts or plans, which allowed them to arrest him without incident.
The other options are incorrect because they do not explain how the police were able to arrest Sobhraj so easily. Option A, toppled over, does not make sense in the context of the question. Option B, bribed, is possible, but it is not the most likely explanation. Option D, threatened, is also possible, but it is not the most likely explanation.
The most likely explanation is that someone gave the police advance information about Sobhraj’s whereabouts or plans. This would have allowed the police to arrest him without incident.