f:R→Rf : \mathbb R \to \mathbb Rf:R→R is C2C^2C2 with f′′(x)>0f''(x) > 0f′′(x)>0 for all xxx, f(1)=1f(1)=1f(1)=1, f(2)=2f(2)=2f(2)=2. Then,
0<f′(2)<10 < f'(2) < 10<f′(2)<1
f′(2)>1f'(2) > 1f′(2)>1
f′(2)=1f'(2) = 1f′(2)=1
f′(2)=0f'(2) = 0f′(2)=0
