Write the negation of the following statement:
$r:$ All birds have wings.

Which of the following statements is/are False?
$S_1: \exists n \in N, \text{ such that } n^2 + n + 2 \text{ is divisible by 4.}$
$S_2: \exists x \in N, \text{ such that } x - 17 < 20.$
$S_3: \forall n \in N, x^2 + 3x - 10 = 0.$
$S_4: \forall n \in N, n^2 \ge 1.$

The negation of the statement "The payment will be made if and only if the work is finished in time" is

The Boolean expression $(p \wedge \sim q) \vee q \vee (\sim p \wedge q)$ is equivalent to:

The statement $(P$ $\Rightarrow Q) \wedge (R$ $\Rightarrow Q)$ is logically equivalent to:

By giving a counterexample,show that the following statement is not true.
$p:$ If all the angles of a triangle are equal,then the triangle is an obtuse-angled triangle.