When doing Torricelli's experiment correctly, the measurement results are related to which of the following factors (　) A. Weather conditionsB. The straightness of the glass tube C. tilt of glass tube

(1) The mercury in the glass tube is supported by the external atmospheric pressure. If there is a vacuum in the tube, the pressure generated by the mercury column in the tube is equal to the atmospheric pressure. Adding more mercury to the mercury tank, tilting the glass tube slightly, changing to a glass tube with a thicker inner diameter, or the straightness of the glass tube will not affect the height of the mercury column.

(2) Weather changes will cause changes in atmospheric temperature. Objects have the characteristics of thermal expansion and contraction. When the temperature changes, the volume will change. The number of air molecules per unit volume changes, so the weather Changes will affect atmospheric pressure.

So choose A.