题目

    Leanne is one of the students studying through online degree programs. She chose to study online for many of the same reasons that other students do. She was working full-time, and did not want to move away from her job and family to continue her education. Leanne liked that she was able to study whenever and however much she wanted.     But while the program met her needs at first, Leanne felt there were things she did not get from studying online. Later, she earned her undergraduate degree from a traditional, face-to-face study program at Thomas Jefferson University.      以下说法正确的是 [　　] A． 纳米材料是指一种称为“纳米”的新物质制成的材料 B． 绿色食品是指不含化学物质的食品 C． 生物固氮是指植物通过叶面直接吸收空气中的氮气 D． 光导纤维是以二氧化硅为主要原料制成的