Asmoothly operating engine depends on a. equal compression between cylinders. b. cylinder compression levels above 100 psi and within 70 psi of each other. c. compression levels below 100 psi on most cylinders. d. high compression on most cylinders.

A. equal compression between cylinders.

Explanation:

Equal compression between cylinders lead to uniform propelling of the shaft which in turn results into smooth motion of the shaft hence a smoothly operating engine.

In case of unequal compression, there shall be experienced unequal propelling which shall in turn result to rough engine  operation

answer; a health care professional;

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