How can 0.0000000028 be expressed in scientific notation?

The correct expression of 0.0000000028 in scientific notation is indeed 2.8 x 10^-9.

To convert a number into scientific notation, the goal is to express it in the form of (m \times 10^n) where (m) is a number greater than or equal to 1 but less than 10, and (n) is an integer. For the number 0.0000000028, you want to shift the decimal point to the right until you reach a position that makes (m) between 1 and 10.

Starting with 0.0000000028, you move the decimal point to the right 9 places to get 2.8. This move to the right indicates a negative exponent in scientific notation because you are dealing with a number smaller than 1. As a result, the exponent is -9. Thus, this can be expressed as 2.8 x 10^-9, which accurately represents the original number in scientific notation.

The other choices do not accurately reflect the proper placement of the decimal or the correct exponent needed for the number provided.