Based on the research conducted by Cialdini, Reno, and Kallgren (1990), which of the following is an effective way to ensure that people don’t litter in public transport?  a. Leave several pieces of...

Based on the research conducted by Cialdini, Reno, and Kallgren (1990), which of the following is an effective way to ensure that people don’t litter in public transport?

 a. Leave several pieces of litter on the bus or train floor.

b. Post signs stating rules of using public transport.

c. Make sure that the bus or train compartment is clean, with only one container of food lying on the floor.

 d. All of the above.