属于多层短语的是（）。
A、前途很光明
B、科学和技术
C、学习汉语
D、伟大而质朴
参考答案：A
One third of our school _________ covered by trees, while the majority of our students ________ girls.
A．is, is
B．are; are
C．is; are
D．are; is
我国的药品标准分为哪四类？各自的含义为何？
