Which of the following has exactly 3 significant figures?

Answer:
A. 0.0451
Explanation:
To determine the amount of significant figures in numbers in science, it is important to follow specific rules:
Option A. 0.0451 has three significant figures: 4, 5, 1.
Option B. 450 has two significant figures: 4, 5.
Option C. 32.10 has four significant figures: 3, 2, 1, 0.
Option D. 370.0 has four significant figures: 3, 7, 0, 0.
Therefore, option A. 0.0451 is the correct answer.