Bubble line chart for more than 3 variables

问题如下：

Which visualization tool is recommended to be used if the goal is to make comparisons of three or more variables over time?

选项：

A.Heat map B.Bubble line chart C.Scatter plot matrix

解释：

A bubble line chart is a version of a line chart where data points are replaced with varying-sized bubbles to represent a third dimension of the data. A line chart is very effective at visualizing trends in three or more variables over time. A is incorrect because a heat map differentiates high values from low values and reflects the correlation between variables but does not help in making comparisons of variables over time. C is incorrect because a scatterplot matrix is a useful tool for organizing scatterplots between pairs of variables, making it easy to inspect all pairwise relationships in one combined visual. However, it does not help in making comparisons of these variables over time.