L'Hospital's Rule may be applied more than once when evaluating x→alimg(x)f(x). After differentiating once, which condition must still hold at x=a to justify taking derivatives a second time?
(a) Both f′′ and g′′ exist and are continuous at x=a
(b) The quotient g′(x)f′(x) is again an indeterminate form 00 or ∞∞
(c) x→alimf′(x)=0 and x→alimg′(x)=0
(d) g′(x)=0 for all x near a but x→alimf′(x)=0