[单选题]
An optic fiber is made o zg82:qbz4,jp7df jntf clea +vs1t0fh,v1y py km(fr plastic with index of refraction of 1.50. For what angle of incidence wy hkfvvy01sm ,tp+1(fill light remain within the plastic "guide"?
A. $>23.4^{\circ}$
B. $>38.3^{\circ}$
C. $>40.3^{\circ}$
D. $>41.8^{\circ}$
