Answer:
Option (B)
Step-by-step explanation:
Primary sources are usually defined as those initial pieces of evidence that are left behind by any observer or participant. This may be letters, diaries, documents, biological as well as audio or visual recordings. These are made in the past.
These sources are highly useful and help in carrying out an investigation and reach the conclusion or to find the criminal. These are most useful in solving crime scenes.
Thus, the correct answer is option (B).