The answer is B. 18.19 cm
To solve this we need to use the formula for the arc lenght.
The formula is:
[tex]Arc=2\pi r(\frac{\theta}{360})[/tex]Where θ is the angle of the arc in degrees.
Now:
[tex]\text{arc}=2\cdot3.14\cdot7.5\cdot(\frac{139º}{360º})=18.1858\approx18.19\operatorname{cm}[/tex]Then, the answer is B.