As there are no choices given I will explain the main reason why Manioc which in popular terms is known as "Cassava" is eaten by people in West Africa.
Manioc or Cassava is a native food found in West Africa and that is part of their daily diet, it is eaten raw as well as roasted and its leaves are also cooked and eaten with boiled rice which in the local language is called "Plasis/Plasas"