Answer:
Population = e. all shark attacks.
Sample = f. the 1000 records of shark attacks that were examined.
Variable = d. the set of groups to which the victims of shark attacks belong.
Explanation:
The population in a particular study refers to the entire set of people to which the research study encompasses, that is all those who are eligible to be a part of the study or those who the study relates to and the outcome of the study Cann be applied to them. In the research study described above, the population of the study is all events of shark attacks.
The sample is a subset of the larger population ; the subset selected in the scenario above is the 1000 records examined out of all the events of shark attacks.
The variable in the study may refer to a set of independent variables which is according to the scenario is the set of groups to which victims of shark attack belong.