______ triangle has all angles less than 90 degrees.
A. obtuse
B. acute
C. isosceles
D. right angled

Hint: We need to find the name of the triangle whose all angles are less than 90 degrees. We will be solving the given question by referring to the definition of the triangle and drawing a figure to get the desired result.

Complete step-by-step solution:
We are asked to find out the name of the triangle whose all angles are less than 90 degrees. We will be solving the given question using the concept of triangles and their properties.
A polygon, in mathematics, is a geometric figure that has a finite number of sides. The sides of any polygon are line segments connected at either end. The point of intersection of two or more points is called the vertex or the corner of the polygon.
The word polygon is composed of two words ‘poly’ meaning many and ‘gon’ meaning sides.
A triangle is one of the basic shapes in geometry. It is a polygon with 3 vertices, 3 edges, and 3 angles.
The properties of the triangle are given as follows,
1. The sum of all the interior angles of the triangle is always equal to ${{180}^{\circ }}$.
2. The sum of the lengths of two sides of a triangle is always greater than the third side.
An acute angle is an angle whose measure is greater than ${{0}^{\circ }}$ but lesser than ${{90}^{\circ }}$ . In simple terms, it is an angle smaller than the right angle.
An acute triangle is a triangle in which all the three internal angles of a triangle are acute.
The diagram of an acute angle triangle is given as follows,

$\therefore$ Option B holds the correct answer for the given question.

Note: In geometry, we should be very careful with the naming conventions of angles, rays, and line segments. A protractor is a tool in geometry used to draw and measure angles. We should be precise while drawing an angle or a line in geometry to get precise results.