Is Corynebacterium Diphtheriae Normally Toxigenic

Is Corynebacterium diphtheriae normally toxigenic?

A) Yes, it always produces a cytotoxin that kills cells in the pharynx.
B) Yes, it always produces a cytotoxin that kills ciliated epithelial cells of the trachea.
C) No, it produces a cytotoxin only when it is infected by a lysogenic bacteriophage that expresses a toxin-producing gene.
D) No, it produces a cytotoxin only when a toxin-encoding plasmid is transmitted via conjugation from another bacterium.