Question

about half of americans have blood type o. this means that this blood type: a is not useful by itself in identifying a suspect b is not important to forensic investigators c is not often found at a crime scene d is not found at crime scenes in other countries

Explanation:

Since about half of Americans have blood type O, it is a common blood type. In forensic investigations, if only blood type O is found (without other more specific evidence like DNA), it cannot uniquely identify a suspect as many people have this blood type. So, blood type O alone is not useful for identifying a suspect.

Answer:

A. Is not useful by itself in identifying a suspect