2. Roughly, it takes light less than 0.000000003 of a second to travel a one-meter distance. Express this number in the form of a × 10^n where 1 < a < 10 and is a one-digit number.
option 1: 3 x 10^8
option 2: 3 x 10 ^-8
option 3: 3 x 10^-9
option 4: 3 x 1-0^9