What is drill? define​

an instrument with an edged or pointed end for making holes in hard substances by revolving or by a succession of blows also : a machine for operating such an instrument. 2 : the act or exercise of training soldiers in marching and in executing prescribed movements with a weapon.

answer; i believe the answer is (biomedical); plz check first good luck

well when looking at this if you think about it   negativley and positivley   react with each other and when the first layer gets full they add layers it starts with 2 on the first layer and it constantly goes on until the official number is there