Voluntary sampling is one type of sampling method that is not probability based. this means that a)each member of a population is equally likely to be chosen for the survey. b)the results of the survey cannot reliably be extended and generalized. c)the likelihood of a member of the population volunteering to be surveyed is not probable. d)the results of the survey are not mathematically probable.

b)the results of the survey cannot reliably be extended and generalized.

Step-by-step explanation:

Voluntary sampling is a type of convenience sample; it is convenient for the researcher to perform.  

However, voluntary sampling can lead to bias; usually only people who feel strongly one way or the other about the survey will volunteer to be members of a sample.

Since there is a possibility of bias, the results of the survey cannot reliably be extended and generalized.

you never say the total so we cant find the percentage used for petrol

step-by-step explanation: