Thickness of a pencil measured by using a screw gauge (least count 0.001 cm ) comes out to be 0.802 cm. The percentage error in the measurement is

Given the thickness ( t) = 0.802m

Least count ( L.C) = 0.001cm

Now, the error in measuring the thickness will be

 (t ± L.C) = ( -0.802 ± 0.001)

Now, the percentage error will be

= 0.001/0.802 x 100%

= 0.1246%

= 0.125%

Thus, option (A) is correct.

Hence, option (A) is correct..