Can we use Radio/Checkbox for mandatory form fields

I am working on designing a website which has admin side fuctionalities involving large number of forms related to creation of sevaral entities within the application along with normal user login. The requirement says there should be an error if mandatory fields are missed while saving the form.

eg. The field Frequency has 3 values to choose from - Daily, Weekly and Monthly.

Option 1

Using a mandatory select input which would have the default value "select" and show and error if not filled on saving the form. Here 2 clicks are required to select a desired option.

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Option 2

Using a radio button and having it defaulted to one of the options (NN/g 's article Radio Buttons: Select One by Default or Leave All Unselected? concludes saying always try to Select One Radio Button by Default). Here, if this field is missed while filling the form no mandatory field error message would be shown.

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Which option would be the correct approach? Is there any alternative solution?

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