The correct answer is C) excessive wear on valves and cylinder liners. Operating a reciprocating air compressor without an air filter will lead to excessive wear on the valves and cylinder liners. This is because the lack of an air filter allows dirt, dust, and other particulates to enter the compressor, causing accelerated abrasive wear on critical moving components. The valves and cylinder liners are especially susceptible to this type of wear, leading to decreased efficiency and shortened service life of the compressor. The other options are incorrect because: A) a clogged air intake would be a symptom of the lack of an air filter, not the cause; B) carbon deposits are more likely to be caused by oil contamination, not just lack of an air filter; and D) excessive discharge pressure is not a direct result of operating without an air filter.