Question

a metric bolt size of m8 means that ____
the bolt is 8 cm long
the bolt is 8mm long
the bolt is 8mm in diameter.
the pitch is 8mm

Explanation:

In metric bolt sizing, the "M" indicates a metric - thread and the number following it represents the nominal outer diameter of the bolt in millimeters. So, an M8 bolt has a diameter of 8 mm.

Answer:

The bolt is 8mm in diameter.