Sorry if this has already been raised before, but search gave no results so far.
I would like to know if it is possible (if so, how?) to have conditional "Thank you" pages based on the choice in the drop-down menu.
E.g. if the drop-down has choice A or C, upon submission of the form, visitor is redirected to http://www.abc.com/ If the drop-down has choice B, redirection goes to http://www.xyz.com?
Yes, you can do that using aliases. Please take a look at our formula engine documentation http://www3.formassembly.com/blog/support-documentation/managing-your-forms/using-formulas/