Recently, health professionals have become concerned about the health effects of biotoxins (indoor damp or mould) in Australia. To investigate the issue, researchers sent factsheets including a link to an online survey to all patients that reported having relevant symptoms (such as asthma, allergic rhinitis, dyspnoea, wheeze, bronchitis), with a history of exposure of indoor damp and mould, at randomly selected primary health care clinics from each state and major territory of Australia. People dwelling in households in Australia are best described as the: Question 4 options: a) Sampling frame b) Study factor c) Study sample d) Population of interest