When I select business as visa type in UK visa application form, it does not give options of visa subtype. without the selection of subtype, I cannot proceed with my application. Please guide.
The visa4uk site probably says something like:
As from 17th October 2018 some visa types will no longer be available on this site. If the visa type you are applying for is no longer available in the lists below, you must apply on the new visa application service.
So you should follow the link and apply on the new website.