Which of the Following Is Not True About Data Manipulation

Which of the following is not true about data manipulation within Tableau Public?

A) You can hide columns that you don't intend to use for any visualizations.
B) Each column is automatically assigned a data type,and you are not allowed to change these.
C) You can create a union of several tables such as Salary2017 and Salary2018 that have the same columns,essentially stacking the data from the tables on top of one another.
D) You can relate (that is,join) tables through primary and key fields; Tableau Public is usually smart enough to detect the relationships.