The surface area of a cylinder is define by the formula S.A.=2πrh+2πr^2, where the first part of the formula refers to the lateral area, perimeter, or circumference and the second part to the area of the bases, which are circles.
On this exercise it is asked to find the lateral area of a cylinder whose radius is 6 cm, and has a height of 20cm. To find the lateral area of the cylinder you should substitute this values into the formula, S.A.=2πrh, and as can be seen the answers are given in terms of π or pi.
S.A.=2πrh
S.A.=2π(6cm)(20cm)
S.A.=2π(120cm)
S.A.=240π cm^2
The lateral area of the cylinder is 240π cm^2 or in other words letter B from the given choices.