Phosphates (e.g., tricresyl, tributyl, tetrabutyl, triphenyl etc.) are added to polymers to act as __________________?

Phosphates (e.g., tricresyl, tributyl, tetrabutyl, triphenyl etc.) are added to polymers to act as __________________?

A. Hardeners
B. Anti-shrinkage agents
C. Plasticisers
D. Transparency improver