Answer:
C. [tex] 2\pi[/tex]
Step-by-step explanation:
Central angle [tex]( \theta) = \frac{\pi}{2} = 90\degree [/tex]
Radius (r) = 4
[tex]l(\widehat{EF}) = \frac{ \theta}{360 \degree} \times 2\pi \: r \\ \\ = \frac{90 \degree}{360 \degree} \times 2\pi(4) \\ \\ = \frac{1}{4} \times 2\pi(4) \\ \\ l(\widehat{EF}) = 2\pi[/tex]
