C. A select control that allows multiple options but has none selected could act like a set of checkboxes (depending on the browser used). However, this question lists a drop-down select control. A drop-down, by default, always passes a value.
A3:
A. FavCountry=CAN,FRA. Because both form controls have the same name, their values are concatenated.
A4:
C. Anything that is sent to the browser (as client-side and auto-generated server-side are) is inherently less secure that manual server-side validation.