In a Study on the Likelihood of Individuals to Litter

In a study on the likelihood of individuals to litter in a public park,______________Coalmine______________(2003) found that the______________increased visitors' likelihood of tossing a flyer onto the ground.

A) presence of trash cans that were visible but rather far away
B) appearance of the person who handed out the flyer was dirty and disheveled
C) presence fewer people nearby to observe the littering
D) appearance of more litter already on the ground