Which of the following is correct?

A module calls (or invokes) another module if the second module triggers execution of the first module. For example, a module that calls a function in another module will cause the function to be executed.

In some cases, a module may use and call another module at the same time. For example, a module that uses a database may also call a function in the database driver.

In conclusion, the correct answer is: C. all of the mentioned.