To express the number 0.000072 in scientific notation, we first need to move the decimal point to the right until we have a number between 1 and 10.
The number 0.000072 can be rewritten as 7.2 x 10^{-5} by moving the decimal point 5 places to the right.
Here’s the number sentence:
0.000072 = 7.2 * 10 ^ -5
Thus, the correct answer is:
7.2 * 10 ^ -5