Universal Set

Q. Which of the following sets can be the universal set for a set of all natural numbers.

1. Set of all real numbers $R$
2. Set of all integers $I$
3. Set of all whole numbers $W$
4. Set of all rational numbers $Q$

Q.

The prefix "milli-" denotes the factor

Q. The universal set of the following sets is
$A$ is set of similar triangles
$B$ is set of right-angled triangles
$C$ is set of equilateral triangles

1. The collection of all angles
2. The collection of all triangles
3. The collection of all straight lines
4. None of these