Answer:
a.JavaScript
Explanation:
<em>Form validation</em> is adopted to prevent the abuse of web form by malicious users, data that are not properly validated causes or leads to security vulnerabilities, thereby making a website to be at a risk of being attacked by malicious users.
<em>Validation rules</em> checks that the data a user enters in a record meets the specify standards before the user is allowed to save the record, a validation rule evaluates the data in one or more fields and return it as true or false.
<em>JavaScript form validation can be used to check all required fields, the steps are adopted are:</em>
<em>i) Basic validation − The form is first checked to make sure that all the mandatory fields are filled.</em>
<em>ii) Data format validation −The data that is entered is then checked for correct form and value before allowing to proceed, submit or save the record.</em>