[单选题]
An optic fiber is made of clear plastic rbru ./fsgq:;with inde/c/kr( h 2ubk 6pfwh6ax of refraction of 1.50. For what angle of incidence will light remain within the plastir(u 6/h2pka chfwb/6 kc "guide"?
A. $>23.4^{\circ}$
B. $>38.3^{\circ}$
C. $>40.3^{\circ}$
D. $>41.8^{\circ}$
