You could start by breaking (t/1000)� down to t� x (1/1000)�.
Now let's become clear about (1/1000)�.
Every time you divide 1 by 1000, you move the 1 three more decimal places to the right of the decimal.
1/1000 = 0.001
0.001/1000 = 0.000001
0.000001/1000 = 0.000000001
0.000000001/1000 = 0.000000000001
So (1/1000)� = 0.000000000001, which has 11 zeros between the decimal and the first non-zero digit.
Dividing a 2 digit number, say 27, divided by 1000� generates a decimal that has 10 zeros between the decimal and the first non-zero digit, as is case in 0.000000000027.
To generate a number that has 7 or fewer zeros between the decimal and the first non-zero digit, you need to divide by (1/1000)� a number with five or more digits, such as 11,111, which when divided by (1/1000)� generates 0.000000011111.
The smallest five digit number is 10,000, which equals 10�.
So any number smaller than 10 will not work for t.
The correct answer is A.
