A：／
B：four
C：fourth
D：forth
7元+3元=____ 8角3分-4角=____
8分+2分=____ 9元3角-2元3角=____
4角6分-6分=____ 7角2分+5分=____
6角+2角3分=____ 3角7分-____分=30分
世界上位置最南的大洲轮廓图是（ ）
- Our head teacher is responsible for his work. He spends most of his time with us.
- ________ He always communicates with our parents in his free time.
一辆质量为m的汽车从静止开始以加速度a启动，经时间t1汽车的功率达到额定功率，再经时间t2汽车速度达到最大vm，以后汽车匀速运动。若汽车运动过程中所受阻力恒为f，则不能求出的物理量（ ）
