Data come in various forms and are measured in different ways. For example, a doctor measures your blood pressure with an instrument, a survey researcher asks you a question and you give a verbal response, you go on holiday to a particular country, you are at a certain age and have a certain income, you have a grade for a completed university course, or this past week you have gone to the supermarket a certain number of times, and bought a certain basket of products, etc. Blood pressure, question response, country, age, income, course grade, number of supermarket visits and purchased products, these are all statistical variables. The observations made on these variables constitute the data. The subjects or individuals or companies on which these observations are made are called cases. Thus, cases might be a group of tourists entering Turkey, for each of whom we have data on which country they come from, how many days they plan to stay in Turkey, what their tourism objectives are (e.g., cultural events, beach holiday, etc.). Or cases might be hospital patients, on whom we have measured the standard medical indicators such as blood pressure, cholesterol levels, blood sugar, and so on.

As also understood from the information given a group of tourist entering Turkey is case, so the correct answer is A. “which country they come from”, “how many days they plan to stay” and “what their tourism objectives are” are statistical variables.