As part of a class project, a college student wanted to estimate the proportion of students at his college that owned a red car. To estimate this proportion he went to a large student parking lot during the middle of a class day. He found that 325 out of 1037 cars (31%) were red. This sample is best described as ______.
a. A volunteer response sampleb. A convenience samplec. A stratified random sample with color of car as the stratad. A simple random sample

A voluntary response sample is a kind of sample that is build up of volunteers. It is mostly biased.
A convenience sample is sample in which elements are chosen on the basis of convenience of researcher.
A stratified sampling is a sampling technique in which researcher divides the entire population into some groups on the bases of some features known as strata and then randomly selects elements from each strata for sample.
A simple random sample is basic sampling method , in which researcher randomly selects elements from population.

Here , the student went to a large student parking lot during the middle of a class day.

Since in the middle of class it is convenient to collect sample of cars from parking lot .

Therefore , the sample is best described a "convenience sample".

Hence, the correct answer is b . convenience sample .