Answer
(a) Al is a main group element, belonging to Group-3A
(b) Br is a main group element, belonging to Group-7A
(c) Mo is not a main group element, belonging to Group-6B
(d) Cs is a main group element, belonging to Group-1A
(e) Pb is a main group element, belonging to Group-4A
Work Step by Step
(a) Al is a main group element, belonging to Group-3A
(b) Br is a main group element, belonging to Group-7A
(c) Mo is not a main group element, belonging to Group-6B
(d) Cs is a main group element, belonging to Group-1A
(e) Pb is a main group element, belonging to Group-4A