To express the number 0.045 as a percent, follow these steps:
1. Understand that "percent" means "per hundred". Thus, converting a decimal to a percent involves determining how many parts out of 100 the decimal represents.
2. To convert a decimal to a percent, multiply the decimal by 100. Mathematically, this is represented as:
[tex]\[
0.045 \times 100 = 4.5
\][/tex]
3. The result from the multiplication is 4.5. Therefore, 0.045 as a percent is 4.5%.
So, among the provided options, the correct answer is 4.5%.