In a regular polygon, all the angles should be same and all the sides should be equal in length.In the given options, only square has all its sides equal and all its angles equal. 

If exactly two sides of a triangle are equal, then the triangle is called an isosceles triangle.

Two right angles = 90${}^{\circ }$ + 90${}^{\circ }$ = 180${}^{\circ }$ = Straight angle.

Let us analyze them:

1. Squares have all angles $={90}^{\circ }$, which is not true for rhombuses.


2. Rectangles have opposite sides equal and all angles $={90}^{\circ }$, true for squares.


3. Rectangles have opposite sides equal and parallel, true for parallelograms.


4. Parallelograms have 4 sides, true for quadrilaterals.


5. Parallelograms may have unequal sides, not true for rhombuses.

So, only 2, 3 and 4 are true.

At 04:30, the angle between the hour hand and minute hand is less than 90^o   and at the other given times, the angle between the minute and the hour hand is more than 90^o.

A line having a fixed/finite length is known as line segment. It can also be defined as a line having two end points. On the other hand, a line having one end point is known as Ray.

Corners of a triangular table which is not a right angled triangle are not perpendicular to each other.

Railway tracks are parallel.

The adjacent walls of a rectangular room are perpendicular to each other, so are the line segments that make 'T'.

Given that
The length of the line segment AB = 5m
The length of the line segment BC = 4m
The length of the line segment AC = 9m
The length of AB+BC = 9m = AC
According to the given conditions, AB + BC = AC. So, B lies in between A and C.

Each Point: 1 Mark
We know that a right angle is equal to 90${}^{\circ }$
a) Any angle less than a right angle is an acute angle.
b) If an angle is greater than 90${}^{\circ }$ and less than 180${}^{\circ }$, then it is called an obtuse angle.
If an angle is greater than 180${}^{\circ }$ then it is called a reflex angle.

Each option: 1 Mark
When the hour hand completes one complete revolution it completes 360 degrees.

a) When the hour hand moves from 3 to 6 it covers 90 degrees. When it moves from 6 to 8 it covers 60 degrees. So, the angle covered when hour hand moves from 3 to 8 is 150 degrees.

Fraction that it has moved = $\frac{150}{360}$ = $\frac{5}{12}$
b) When the hour hand of the clock moves from 3 to 9 it moves through two right angles.
So the angle it covers when it moves from 3 to 9 = 180 ${}^{\circ }$
Fraction that it has moved = $\frac{180}{360}$ = $\frac{1}{2}$