Consider the following relational diagram. Which of the below-listed attributes can be expected to be unique, le, not have duplicates? Entity_1 PK el_id PK Entity_2 e2_id att_e2_a el_id att_el_a att_e1_b FK1 Those that are identified as PK Oeld of Entity. 1. 2. ld of Entity 2. and elld of Entity:2 None of the attributes are expected to be unique, since none of them have unique specified All attributes are expected to be unique, since relations don't allow duplicates