In a form, user have an option to choose the submission type. Based on the selected submission type, user should get an option to choose sub-type. Please let me know how this is done in Drupal 7. Please suggest a module.
If user select e-book, sub-type should change to case:1 (see image)
If user select e-project, sub-type should change to case:2
If user select e-lab manual, sub-type should change to case:3
Seems like you are looking for Conditional Fields module...
Conditional Fields allows you to manage sets of dependencies between fields. When a field is “dependent”, it will only be available for editing and displayed if the state of the “dependee” field matches the right condition. When editing a node (or any other entity type that supports fields, like users and categories), the dependent fields are dynamically modified with the States API. You can, for example, define a custom “Article teaser" field that is shown only if a "Has teaser" checkbox is checked.
See below image displayed in project page which suits your requirement.. Hope above module solves your problem..
If this is taxonomy term based, try using Simple hierarchial select. Details from project page:
Simple hierarchical select defines a new form widget for taxonomy fields to select a term by "browsing" through the vocabularies hierarchy. The widget is available in node forms and as Views exposed filter.
This module has been inspired by Hierarchical select but is much simpler.
It provides a field widget that can force deepest level selection, so your nested terms are fully utilized.
