Ok a actually have two questions..
1. Which of the following expressions is written in scientific notation?
a) 73.4x10^5
b) 0.09x10^7
c) 80x10^3
d) 4.22x10^-3

2. Which of the following is 0.0000000708 written in scientific notation?
a) 7.08x10^-8
b) 7.8x10^-8
c) 708x10^-10
d) 70.08x10^-9

Respuesta :

1.  d) 4.22x10^-3 or b) 0.09x10^7
2. a) 7.08x10^-8

Hope this helps!
Scientific notation requires the number before multiplication with 10 be between 1 and 9 (inclusive).
Therefore, the correct options are:

1) D.
2) B.