As shown in the figure, the steelyard is a traditional tool for measuring quality, in which A and B are two knobs with different ranges. The measured object is hung on the hook C of the steelyard, and

As shown in the figure, the steelyard is a traditional tool for measuring quality, in which A and B are two knobs with different ranges. The measured object is hung on the hook C of the steelyard, and the knob A is lifted. A, because the weight arm of the weight is greater than the weight arm of the measured object, the object with a mass greater than the weight can be measured. So, A is wrong.

B. When the button A is pressed, the arm of the measured object is smaller than when the button B is pressed, and its range is larger. Therefore, B is correct.

C, to reduce weight, it is necessary to increase the arm, the index is too big. So, C is wrong.

D, the scale has balanced the influence of beam gravity on time, which is very good. So, d is wrong.

So choose: B.