The basic functioning of WTO depends upon: 1. Multifiber Agreement (MFA) 2. Agreement on Agriculture (AoA), Trade Related Investment Measures (TRIMS), Trade Related Intellectual Property Right (TRIPS), General Agreement on Trade and Services (GATS). Multilateral Agreement on Investment is among OECD countries.
Reference: https://www.wto.org/index.htm
So, the correct answer is $(C).$