Concept:The word "deleterious" refers to something harmful or damaging in effect.
Explanation:The correct meaning of "deleterious" is causing harm or damage.
Option A, "effecting a deletion," relates to removing something, not causing harm.
Option B, "an untrue proposition," describes a false statement, which is unrelated to harm.
Option C, "causing harm or damage," correctly defines the intended meaning of the word.
Option D, "the process of deletion," is similar to Option A and does not match the meaning.
Therefore, the option that best expresses the meaning of "deleterious" is Option C.
Answer:C. Causing harm or damage