For choosing multiple options within a drop down use the ctrl+left click.
1. query: Get all NMR structures that have base modifications
Select Base modification and NMR by choosing yes next to them.
Choosing the option AND next to both will narrow down your search and output only those structures that satisfy both the options.
note: Choosing the option OR will list all NMR structures and all structures with base modification.
2.query: Get all structures with Minor groove binders
When querying for a particular drug binding type like Minor groove binders check yes to both ligand and drug and then click on Minor groove Binder to get all structures with minor groove binders.