No tab stops should be used in any source code submissions. If used on the original, conversion to spaces should be done for submission. Tab stops vary with editor, and cannot be guaranteed when transferred from one machine to another.
Projects are graded partly on documentation and style, so consistency is important.
Functional indentation should be used in all control structures. Indentation stops should be consistent and should be 3 or 4 horizontal spaces. Parameter overflow should be lined up under the first parameter. Overflow should be lined up under the opening parenthesis. This is for consistency.