What Sampling Problems Arise Through the Use of Online Surveys

What sampling problems arise through the use of online surveys as the survey method?

A) Obtaining a cross-sectional sample can be severely restricting, as Internet users tend to be from more younger and affluent groups in society
B) The sample is too broad to be representative. The Internet allows for responses from anywhere in the global, therefore increasing the difficulty in analysis
C) Samples are usually too low to make inferences on the general population
D) Samples are too large, making analysis difficult