A:导电性
B:抗腐蚀性
C:导热性
D:延展性
① Time for breakfast. ____ A. Sing and dance.
② Time for PE class____ B. Drink some milk.
③ Time for English class ____ C. Read and write.
④ Time for music class. ____ D. Jump and run.
下面是某同学进行历史探究学习时设计的年代尺,你能推断他探究的主题是( )