Universal Containers wants to ensure that they are accepting clean data from their users and...

The correct answer is C.

Universal Containers wants to accept clean data and verify that important fields are entered. The best solution is a validation rule, because validation rules verify that data entered by users meets defined standards before the record can be saved. This is stronger than making a field required only on a page layout, because validation rules can enforce requirements based on conditions such as record type.

A is weaker because page-layout required fields apply mainly to that UI layout and do not provide the same conditional data-quality enforcement. B is reactive cleanup after bad data exists. D can calculate or display a value, but it does not enforce user data entry by itself.

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