ANSWER
[tex] \frac{3\pi}{4} \: radians[/tex]
EXPLANATION
To convert an angle from degrees measure to radians, we multiply by:
[tex] \frac{\pi}{180 \degree} [/tex]
We want to convert 135° to radians.
This implies that,
[tex]135 \degree = 135\degree \times \frac{\pi}{180 \degree} = \frac{3\pi}{4} \: radians[/tex]
The last option is correct.