(A) 7 periods and 18 groups
(B) 8 periods and 7 groups
(C) 7 periods and 7 groups
(D) 8 periods and 8 groups
The answer is (A) 7 periods and 18 groups
(A) 7 periods and 18 groups
(B) 8 periods and 7 groups
(C) 7 periods and 7 groups
(D) 8 periods and 8 groups
The answer is (A) 7 periods and 18 groups