The term that describes an increase in earnings per share or a decrease in loss per share due to the conversion of convertible instruments, exercise of options or warrants, or issuance of ordinary shares upon meeting specific conditions is the definition of "Dilution" in the context of earnings per share calculations. Therefore, the correct term in this case would be:

C. Put options

However, it seems there might be a misunderstanding in the question. The term "Put options" typically refers to a type of derivative contract that gives the owner the right to sell (or "put") the underlying asset back to the writer of the option at a predetermined price within a specific time frame. In the context of earnings per share calculations, put options do not directly relate to the dilution of earnings per share. The dilution refers to the decrease in earnings per share due to the potential conversion of convertible instruments, options, or warrants, as mentioned in the question. So while "Put options" (option C) may not be the most accurate choice here, the concept described in the question is indeed about dilution, which is represented by option A, "Antidilution" was likely meant to be the opposite of what was listed.