roll toy cars across each bridge until it collapses place concrete construction blocks on top of each bridge until it collapses stack coins on both ends of each bridge until it collapses place D-cell batteries at the center of each bridge until it collapses
I gave my students this multiple choice question: Several students are entering a bridge building contest that requires using ice cream sticks and glue to construct the strongest bridge possible. The bridges must be 5 in. wide and span a length of 18 in. Which of the following tests is the most accurate way to determine the strongest span design for these bridges?

Only one answer is correct among these 4 choices:
- roll toy cars across each bridge until it collapses
- place concrete construction blocks on top of each bridge until it collapses
- stack coins on both ends of each bridge until it collapses
- place D-cell batteries at the center of each bridge until it collapses

Could you tell me which one is correct?

place D-cell batteries at the center of each bridge until it collapses