Q$1.$ Choose the correct answer from the following

$[2\mathrm{.}2][2]$

In order for two queries to be UNION$-$compatible, they must:

A$)$ both have the same number of lines in their SQL statements.

B$)$ both output compatible data types for each column and return the same number of rows.

C$)$ both return at least one row.

D$)$ both return exactly one row.

Answer: