The correct answer is C. gvisTreeMap.
A tree map is a hierarchical data visualization technique where each node in the tree is represented by a rectangle whose area is proportional to the value of the node. Tree maps are often used to visualize data that is hierarchical in nature, such as the population of countries or the sales of products by category.
gvisTreeMap is a Google Visualization API function that can be used to create tree maps. It takes a data set as input and returns a tree map as output. The data set must be in a specific format, which is described in the gvisTreeMap documentation.
gvisGeoChart is a Google Visualization API function that can be used to create geo charts. It takes a data set as input and returns a geo chart as output. The data set must be in a specific format, which is described in the gvisGeoChart documentation.
gvisTable is a Google Visualization API function that can be used to create tables. It takes a data set as input and returns a table as output. The data set must be in a specific format, which is described in the gvisTable documentation.
Therefore, the only function that can be used to create tree maps is gvisTreeMap.