Which of the following scenarios demonstrates sampling bias? (a) to estimate the ethnic background distribution of residents of his town, adam collects data from 1000 randomly selected town residents by using a random number generator. (b) lisa wants to estimate the male to female ratio of the residents of her city. she collects data by recording the sex of every soth resident after selecting a random starting point on a list of residents (c) jean wants to estimate the mean amount of money spent on clothes per week by mall shoppers. she collects data from every 10th person entering a clothing store at the mall.(d) to estimate the mean number of classes that students take at his university, frank collects data from a randomly selected proportionate number of students from each grade level.