Properties of Union of Sets

Q. For any three sets $X,Y\&Z;(X\cup Y)\cup Z=$

1. $X\cup (Y\cup Z)$
2. $X\cup (X\cup Z)$
3. $Y\cup (Y\cup Z)$

Q. The commutative law states that for any two sets $X\&Y;X\cup Y=Y\cup X.$

1. False
2. True

Q. For any two sets $A\&B,A\subset B,A\cup B=$

1. $A$
2. $B$
3. $\left\{\right\}$

Q. For any two sets $A\&B,A\subset B,A\cup B=$

1. $A$
2. $B$
3. $\left\{\right\}$

Q. Write down all possible subsets of the following set:
(i) {a}

Q. For any set $M$ if $M\cup \varnothing =\varnothing ,$ then

1. $M=\varnothing$
2. $n\left(M\right)=1$
3. $n\left(P\right(M\left)\right)=2$

Q. For any set $A$ for which $U$ is the universal set, $A\cup U=A.$

1. False
2. True