LenoxSoft wants to provide a list of their products on their "Contact Us" form and...

 If LenoxSoft wants to provide a list of their products on their “Contact Us” form and ask prospects to select only one product they are most interested in, they should leverage the dropdown field type. A dropdown field is a single-select field that allows the prospect to choose one option from a predefined list. A dropdown field can be used to capture information such as product interest, industry, or country. A dropdown field can also be used as a controlling field for dependent fields5. References: Marketing Cloud Account Engagement Form Field Types