F'(x)>0, and f'(x) is monotonically decreasing, so f(x) should be monotonically increasing and convex;

G'(x)>0, and g'(x) rises monotonically, so g(x) should rise monotonically and be downward convex;

In addition, if f'(x0)=g'(x0), we know that the tangent slopes of functions f(x) and g(x) at x0 are equal, so we choose d.