A triangular prism has a triangle base with sides 8, 15, 17 units and height 20 units. Its total surface area is:

A triangular prism has 5 faces:

2 triangular faces and 3 rectangular faces.

Surface area of a prism:

= Area of the 2 triangle of the prism + area of the 3 lateral rectangular parts

Area of the 2 triangle of the prism:

Triangle with sides 8, 15 and 17 units is a right-angled triangle with the height of 15 units.

Area of the 2 triangles = 1/2 ×bh × 2

= 1/2 × 8 × 15 × 2

= 120

Surface area of the 2 triangular parts is 120 units²

Area of the 3 lateral rectangular parts:

The rectangles have area of:

8 units by 20 units, 15 by 20 units and 17 by 20 units.

Area of the rectangular parts:

(8 × 20) + ( 15 × 20) + ( 17 × 20)

= 160 + 300 + 340

= 800 units²

The total area of the triangular prism thus is:

120 units² + 800 units² = 920 units²

Total surface area of the triangular prism = 920 units²

C is correct choice.