Final answer:
The ratio of students to teachers is 11.5:1, which rounds down to an approximate whole number ratio of 11:1, making Option 2 the most accurate selection.
Step-by-step explanation:
The ratio of students to teachers on a field trip with 138 students and 12 teachers is found by dividing the number of students by the number of teachers. To find this ratio, we perform the following calculation:
138 ÷ 12 = 11.5
Since we cannot have half a person, when expressing this as a ratio, we round down to the nearest whole number. Therefore, the ratio is 11:1, which means for every teacher, there are 11 students approximately. The precise ratio, considering decimals, would actually be 11.5:1, but ratios typically use whole numbers, so the correct option would be that nearest to the actual decimal value.
Option 2: 11:1 is, thus, the most appropriate answer given the closest whole number approximation.