Final answer:
The student could not use a line graph to display her results because line graphs are used to show the relationship between two or more variables over a continuous interval. So the correcct answer is Option C.
Step-by-step explanation:
The student could not use a line graph to display her results because line graphs are used to show the relationship between two or more variables over a continuous interval. In this case, the number of siblings is a categorical variable, so it doesn't make sense to represent it on a line graph.
A better option would be a bar chart or a pie chart. A bar chart would show the number of siblings for each person, while a pie chart would show the percentage of people with different numbers of siblings.
A scatter plot would not be a suitable way to display the results because it is used to show the relationship between two continuous variables, such as height and weight, rather than categorical data like the number of siblings.