Final answer:
Option B, referring to the beating of a shop owner by four alleged immigrants, is the evidence that details the cause of the riots.
Step-by-step explanation:
The piece of evidence from the text that details what may have caused the riots to occur is option B: "The outburst was triggered by the severe beating of a shop owner by four alleged Venezuelan immigrants on Friday" (Paragraph 5). This statement clearly identifies a specific inciting event that led to the social unrest and subsequent rioting. Unlike the other options, which describe the aftermath of the riots or responses to the riots, this piece of evidence points to an actual event that sparked the unrest. It indicates a cause-and-effect relationship between the beating of the shop owner and the outbreak of violence.