The correct option is B 1,000,000,000
In 109,
∙Base=10
∙Exponent=9
We know the exponent to the base 10 defines the number of zeros after 1 when writing the number.
Here, in 109, as the exponent is 9, we include 9 zeros after 1 when writing 109 in number form.
∴109=1,000,000,000
(1,000 Million or 1 Billion)
Hence, option (b.) is the correct one.