Step 1: Calculate the angle at 6:00.
At 6:00, the hour hand is at the 6th hour mark, which corresponds to an angle of:
\[
\text{Angle} = 30^\circ \times 6 = 180^\circ
\]
Step 2: Calculate the position of the minute hand.
At 6:30, the minute hand is at the 6th minute mark, which is:
\[
\text{Angle of minute hand} = 30^\circ \times 6 = 180^\circ
\]
Step 3: Find the angle between the hands.
The angle between the hour and minute hand is the absolute difference between the angles:
\[
|195^\circ - 180^\circ| = 15^\circ
\]
Thus, the angle between the hands at 6:30 is 135°.
Step 4: Conclusion.
Thus, the correct answer is \( \boxed{135^\circ} \).