What is a template in C++ primarily used for?

A template in C++ is primarily used to reuse source code with different data types. This means that instead of writing new code for each data type, a single template can be defined and used to generate different versions of that code for each data type. This increases efficiency and reduces the risk of errors in the code. Options A and C are not correct because templates do not directly impact the error-free-ness of code or the speed of compilation. Option D is also incorrect as virtual functions and templates serve different purposes in C++.