Final answer:
Carl used 72% of a tank of gasoline, which is represented as 0.72 in decimal form or 72% as a percent, indicating that the correct answer is A. 0.72 or 72%.
Step-by-step explanation:
If Carl used 72% of a tank of gasoline going to Houston, the decimal and percent that represent this amount are 0.72 or 72%. Therefore, the correct answer is A. 0.72 or 72%. To convert a percentage to a decimal, you divide the percent by 100. So in this case, 72% divided by 100 equals 0.72.