亚共析钢的室温组织由（）和（）构成。
参考答案：铁素体；珠光体
My brother once studied in America for three years, so he can English very well. [ ]
A. talk
B. speak
C. say
D. tell
中药茵陈、前胡、秦皮中主要的有效成分为香豆素类。（）
