Answer: Stand the children in line, going over the safety rules and regulations for field trips.
Amongst all the options listed above, the best option is for the student teacher to "Stand the children in line, going over the safety rules and regulations for field trips". This is because that is the only option that involves prepping the children for the field trip. Standing them in line, makes them ready for the trip, going over the safety rules and regulations makes them alert and active for what they are to expect. Every other option will take their mind away form the trip which is not a good method for prepping.