题目

Homestay in Sydney, AustraliaLinda:Our big home is in Sydney, about 300 meters from Sydney University and 450 meters from the train station. The train ride is about 30 minutes to the CBD. Now we only have a small bedroom for a female student.The cost is $260 per week, which includes all meals when at home and laundering(洗烫) of clothes.E-mail: markalarms @optusnet. com.auJohn:I have a lovely single room for homestay (male, non-smokers only). The apartment is located across the road from a bus station. A sports field is only a two-minute walk away.The room is for both short and long stays. T4．物体甲、乙原来静止于光滑水平面上．从t=0时刻开始，甲沿水平面做直线运动，位移x和时间平方t2的关系图象如图甲；乙受到如图乙所示的水平拉力F的作用．则在0～4s的时间内（　　）A．甲物体所受合力不断变化B．2s末乙物体速度达到最大C．2s末乙物体速度为0D．2s末乙物体改变运动方向E．甲物体的速度不断减小