Answer:
Option A is correct, i.e. 4.5*10^-3
Explanation:
To write scientific notations:-
1. The first digit should be non-zero.
2. The decimal representation should be a number greater than 1 and less than 10.
3. The exponent representation should be in form of 10's power.
Checking given options:-
B. 14.5*10^2
Given option B has decimal representation greater than 10, so it is NOT correct.
C. 0.78*10^-6
Given option C has decimal representation less than 1, so it is NOT correct.
D. 5.7*4^8
Given option D has exponent representation NOT in form of 10's power, so it is NOT correct.
Checking option A:- 4.5*10^-3
Given option A has decimal representation between 1 and 10. Also it has exponent representation in form of 10's power.
Hence, option A is correct, i.e. 4.5*10^-3