Determine whether the sampling method mentioned below appears to be sound or is flawed. Give a reason.
A total of 1,500 individuals participated in an online survey on a health-focused website. The question posed was: 'Do you consider organic foods to be healthier than non-organic foods?' The respondents were site visitors who opted to take part in the poll.

The sampling method is sound because 1,500 respondents provide a large enough sample size.

The sampling method is flawed because it considers the results of an online survey.

The sampling method is flawed because it does not ensure a random, representative sample.

The sampling method is flawed because it did not include an equal number of respondents who prefer organic and non-organic foods.