The combined correction for curvature and refraction can be given as _

1.	The combined correction for curvature and refraction can be given as _______
A.	C = 14d<sup>2</sup>/6R
B.	C = 6d<sup>2</sup>/7R
C.	C = 7d<sup>2</sup>/2R
D.	C = 6d<sup>2</sup>/14R
Answer» E.

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