Solution:
Given:
Scientific notation is a way of writing very large or very small numbers.
A number is written in scientific notation when a number between 1 and 10 is multiplied by a power of 10.
Hence, we move the decimal points such that the number is between 1 and 10 and then multiply it by a power of 10.
Thus,
Hence, the decimal point was moved 7 times to make the number fall between 1 and 10.
The number becomes 7.84 and the power of 10 to which is multiplied is 10 to power 7 because the decimal was moved 7 times.
Hence,
Therefore, option B is correct.