For each calculation choose the correct answer written in standard form.
a) (7 * 10°) ~ (3 x 10?)
A
B
21 x 100 21 x 10
С
2.1 x 10"
D
2.1 x 10
b) (2 x 10°) = (4 x 102)
A
2 x 10
B
5 x 10
с
0.5 x 10
D
2 x 10