Food safety and human health

A kind of food smoked with sulfur, such as tremella and vermicelli, contains substances harmful to human body, so the choice is wrong;

B, the food pickled with industrial salt containing sodium nitrite is harmful to human body, so the option is wrong;

C, using dry ice can preserve perishable food, which is harmless to human body, so the option is correct;

D, using "lean meat" as feed additive will harm human health, so the choice is wrong;

So choose C.