Explanation

The International Institute of Tropical Agriculture (IITA) has its headquarters in Ibadan, Nigeria. However, the question asks for the location of the institute, and while it operates in many countries, its main headquarters is in Nigeria. Wait, let me double-check. The IITA was founded in 1967 and its headquarters is indeed in Ibadan, Nigeria. Therefore, B should be the correct answer. The current answer A (Mexico) is incorrect.