To answer this question, you need to understand the concept of a sentinel value.
A sentinel value is a special value that is used to indicate the end of a sequence or list of data. It is used to signal that there is no more data to be processed.
Option A) A sentinel value is not specifically used to prevent infinite loops. It is used to indicate the end of data, but it does not directly prevent infinite loops.
Option B) A sentinel value does not have to be a negative value. It can be any value that is chosen to represent the end of the data.
Option C) This option is correct. A sentinel value signals the end of a list of data.
Option D) Option D is incorrect because a sentinel value does not have to be a negative value. Therefore, both a and b are not always true.
Option E) Option E is incorrect because not all of the above options are correct. Only option C is correct.
The correct answer is C. This option is correct because a sentinel value is used to signal the end of a list of data.