Properties of Union of Sets

Q. For any set $A,A\cup A=A.$

1. False
2. True

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

1. False
2. True

Q. Any set $A$ such that $A\cup A=\{11,13,5,6\},$ then $A=$

1. $\{11,13,5,6\}$
2. $\{5,6\}$
3. $\left\{\right\}$

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 $X,X\cup \varnothing =X.$

1. False
2. True

Q. Three sets $A,B\&C$ such that $A\subset B,$ then $A\cup (B\cup C)=$

1. $B\cup C$
2. $A\cup C$
3. $B$

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

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