The following phenomena are not caused by atmospheric pressure: (a) sucking drinks into the mouth with a straw; (b) sucking a large piece of glass with a sucker; (c) Use a hydraulic jack.

A. When drinking through a straw, suck the air out of the straw first. Under the action of external atmospheric pressure, soda water is pressed into the straw, so this item does not meet the meaning of the question.

B. When the suction cup is pressed against the glass, it is necessary to squeeze the suction cup hard to squeeze out the air in the tray, and then the suction cup is pressed against the glass by the external atmospheric pressure, so this item does not meet the meaning of the question;

C, using hydraulic jacks to support heavy objects, which uses the knowledge of liquid pressure, that is, this option does not use atmospheric pressure, so this option meets the meaning of the question;

D, in the working process of the pump, the air pressure in the pump is reduced, that is, the external atmospheric pressure is greater than the internal air pressure of the pump, and the water is pressed into the pump under the action of the external atmospheric pressure, and then reaches a high place, so this option does not meet the question.

So choose C.