Answer:
A and C
Explanation:
A. \
(4.0 x 5.0)(10^3 x 10^5)
20 x 10^8
2.0 x 10^9
B. doesn't work, do not understand last number
C.
(2.1 + 2.7) (10^5 + 10^5) since powers are the same, do not need to change anything
4.8 x 10^5
D.
(3.1 - 2.7) (10^5 - 10^2) since powers are not the same, you need to make them equal
Do not need to subtract powers, hence D is untrue