It is given that,

Each side of an equilateral triangle, a = 8 cm

We know that,

Area of equilateral triangle =

=

= × 64

=

= 16 cm²

Also,

Area of triangle =

16 = × a × Altitude

∴ Altitude =

= 4 cm

Hence, altitude of the triangle is 4 cm

Thus, option (c) is correct