Answer: B. 3.99 ⋅ 10^−6
Step-by-step explanation:
The number that is the smallest has the smallest power of 10.
If we convert the possible answers to ordinary numbers, it will be clearer.
A. 4.4 ⋅ 10^−5 = 0.000044
B. 3.99 ⋅ 10^−6 = 0.00000399
C. 2.6 ⋅ 10^2 = 0.026
D. 1.85 ⋅ 10^3 = 0.00185
