In the modern long-form of periodic table, the horizontal rows and the vertical columns are called as __________ and ___________ respectively.

In the modern long-form of periodic table, the horizontal rows and the

1.	In the modern long-form of periodic table, the horizontal rows and the vertical columns are called as __________ and ___________ respectively.
A.	groups, periods
B.	periods, groups
C.	rows, columns
D.	columns, rows
Answer» C. rows, columns