It is given that the figure can be formed in the shape of the die, as we know that the sum of numbers on opposite faces of a die is 7.
When we will form a die with the given shape the number on the opposite face of A is 2.
$⟹$ A + 2 = 7
$⟹$ A  = 7 - 2
$⟹$ A  = 5

Number of faces (F) = 9

Number of edges (E) = 16

Number of vertices (V) = 9
So F = V

From the figure,

a die can be made.

In a die, the sum of numbers on opposite faces is 7.

So, 3+2+1+A+B+C = 7×3

So, A+B+C = 15. 

This shape has a triangular base, and the sides are made from 3 triangles which meet at the top. The resultant shape is a pyramid.

Explanation: 1 Mark each
(i) A prism becomes a cylinder when the number of sides increases.
(ii) When the number of sides of the pyramid increases, it becomes a cone.

Definition: 1 Mark each
An Oblique sketch does not have proportional lengths, still, it conveys all important aspects of the appearance of the solid.
An Isometric Sketch is drawn on an isometric dot paper. In an isometric sketch of the solid, the measurements are kept proportional.

Examples: 0.5 Marks each
Few examples of prisms are:
a) Triangular prism
b) Hexagonal prism
c) Cuboid
d) Cube

Answer: 1 Mark
Key feature: 1 Mark
A cuboid has 6 faces which are all rectangles.
Cuboid is a rectangular prism.
The key feature of a prism is that it has a rectangular cross-section along its length. The cuboid also has a rectangular cross-section, which makes it a prism.

Definition: 1 Mark each
a. A vertex (plural: vertices) is a point where two or more straight lines meet. E.g. The 8 corners of the cube are its vertices.
b. An edge is a line segment that joins two vertices. E.g. The 12 line segments that form the skeleton of the cube are its edges.
c. A face is any of the individual surfaces of a solid object. E.g. The 6 flat square surfaces of the cube are its faces.