Final answer:
The most common mode of transmission of STEC is ingestion of contaminated and undercooked meat.
Step-by-step explanation:
The most common mode of transmission of STEC (Shiga toxin-producing Escherichia coli) is ingestion of contaminated and undercooked meat. This includes raw or undercooked ground beef, as well as raw or undercooked poultry and dairy products. It is important to properly cook meat to kill any potential bacteria and prevent foodborne illnesses.