Find all the values of t so that 9^eBt > 0

Find all the values of t so that 9eBt > 0?

1. t > 1/9
2. -∞ < t < ∞
3. 0 < t < ∞
4. t < 1/9

Since exponential function y = a^x is always positive, the answer is -∞ < t < ∞