44. B 事实细节题。根据文章中的“Firstly,...Fourthly,...”可知,作者给出了读者四条建议。故选B。
45. C 事实细节题。由作者给出的第二条建议中“A good way to test your understanding is to explain a concept to a classmate or someone else.”可知,测试你理解力的一个好方法是向一位同学或者其他人解释一个概念,故选C。
46. B 事实细节题。由文章最后一段“It's often used in daily life just like math and physics.”故A选项错误;由第一段中第三行“At first, studying chemistry is like learning a new language.”故C选项错误;由于第一自然段第一句话“Chemistry is usually thought to be more difficult than other subjects, at least for the beginners.”故D选项错误;由第一自然段三、四行“Also, some concepts(概念)of chemistry are hard to understand.”可知,一些化学上的概念是难理解的, 故选B。
47. D 主旨大意题。本文主要介绍了化学学科的学习方法,所以文章的大意应为选项D,学生如何学习化学。