In paragraph 5 (“Cassava . . . east Africa”), the author includes the detail that cassava is “already the fourth most important source of daily calories” in sub-Saharan Africa mainly to Responses illustrate that cassava is a significant part of the diet in some communities. Answer A: illustrate that cassava is a significant part of the diet in some communities. A emphasize that cassava can serve only as a limited substitute for other crops. Answer B: emphasize that cassava can serve only as a limited substitute for other crops. B suggest that cassava is a healthier alternative to wheat flour. Answer C: suggest that cassava is a healthier alternative to wheat flour. C acknowledge that cassava can be grown only in sub-Saharan Africa.