In a binary relation two elements are chosen from the set. So, with $n$ elements $n^2$ pairings are possible. Now, a relation can be any subset of these $n^2$ pairings and thus we get $2^{n^2}$ binary relations.

Let $L$ be a set with a relation $R$ which is transitive, anti-symmetric and reflexive and for any two elements $a, b \in L$, let the least upper bound $lub (a, b)$ and the greatest lower bound $glb (a, b)$ exist. Which of the following is/are true? $L$ is a poset $L$ is a Boolean algebra $L$ is a lattice None of the above

Mr. X claims the following: If a relation R is both symmetric and transitive, then R is reflexive. For this, Mr. X offers the following proof: “From xRy, using symmetry we get yRx. Now because R is transitive xRy and yRx together imply xRx. Therefore, R is reflexive”. Give an example of a relation R which is symmetric and transitive but not reflexive.

Let $G$ be a finite group and $H$ be a subgroup of $G$. For $a \in G$, define $aH=\left\{ah \mid h \in H\right\}$. Show that $|aH| = |bH|.$ Show that for every pair of elements $a, b \in G$, either $aH = bH$ or $aH$ and $bH$ are disjoint. Use the above to argue that the order of $H$ must divide the order of $G.$

Which of the following is/are correct? An SQL query automatically eliminates duplicates An SQL query will not work if there are no indexes on the relations SQL permits attribute names to be repeated in the same relation None of the above