【正确答案】 A

【答案解析】[解析] In the Nile Valley ten thousand years ago, the people used stones to crush grain into coarse flour. Then they turned the flour into primitive forms of bread. Primitive bread wasn't like the bread we know today; it was simply flour dough dried on heated stones. The invention of ovens came later. Leavened breads and cakes, which are made to rise by the action of yeast, were also a discovery of the ancient Egyptians. The Egyptians were the first people to master the art of baking. News of this new wonder food spread to other places in the Middle East. Soon other people were collecting seed, cultivating land, and inventing ways to turn grain into flour. What does the professor mainly discuss? The professor mainly discusses the origins of bread. She says: ...primitive forms of bread. Primitive bread wasn't like the bread we know today...; Leavened breads and cakes.., were also a discovery of the ancient Egyptians; News of this new wonder food spread