Most Modern Systems Have Only Two Beep Codes to Indicate

Most modern systems have only two beep codes to indicate something is wrong.What are they?

A) One short beep followed by a continuous set of long beeps and a continuous set of short beeps
B) One long beep followed by two or three short beeps and a continuous set of short beeps
C) A continuous set of short beeps and a series of three long beeps followed by one short beep
D) A continuous set of long beeps and three short beeps followed by one or two long beeps