Where Is the Curve X = Ln T, Y = $\le$

Where is the curve x = ln t, y = e^t concave upward?

A) at all points on the curve
B) at all points corresponding to values of t satisfying t > 1
C) at all points corresponding to values of t satisfying 0 < t < 1
D) at all points corresponding to values of t satisfying 0 < t $\le$ 1
E) nowhere