The following eight structures have been tested for activity as kinase inhibitors. Five structures are active and three are inactive. Assess the structures and choose the features that might be required for the activity. Select one or more: Hydrogen bond acceptor feature at position 6 Hydrogen bond donor feature at position 3 Donor/acceptor feature at position 1 Aromatic feature at position 2 Hydrogen bond acceptor feature at position 4 Aromatic feature at position 5