Answer
a) Bk, b) Br, c) B, d) Ba, e) Br
Work Step by Step
According to the periodic table B - Boron is a metalloid, Ba - Barium is an alkaline earth metal, Bi - Bismuth is from group 5A, Br - Bromine is liquid at room temperature, and also Bk - Berkelium is the only radioactive element among these five, so:
a) Bk, b) Br, c) B, d) Ba, e) Br