The correct answer is: B. neutralizes the effect due to pull and sag.
Normal tension is the tension in a tape that is applied perpendicular to the tape’s length. It is used to neutralize the effect of pull and sag, which are two factors that can affect the accuracy of a tape measure. Pull is the force that is applied to the tape when it is being used to measure something. Sag is the tendency of the tape to droop when it is not being held taut. Both pull and sag can cause the tape to measure incorrectly. Normal tension helps to minimize the effects of pull and sag by applying a force that is perpendicular to the tape’s length. This helps to keep the tape straight and prevents it from drooping.
Option A is incorrect because normal tension is not used at the time of standardising the tape. The tape is standardized by applying a known force to it and then measuring its elongation. This is done to ensure that the tape is accurate.
Option C is incorrect because normal tension does not make the correction due to sag equal to zero. The correction due to sag is a function of the tape’s length, its material, and its weight. Normal tension does not affect these factors, so it cannot make the correction due to sag equal to zero.
Option D is incorrect because normal tension does not make the correction due to pull equal to zero. The correction due to pull is a function of the tape’s length, its material, and its weight. Normal tension does not affect these factors, so it cannot make the correction due to pull equal to zero.