氧气在空气中含量为（），有明火或剧烈震动，容易发生爆炸
A.10%～20%
B.15%～27%
C.4%～75%
D.大于50%
参考答案：B
如图小船在200m宽的河中横渡，水流速度为2m/s，船在静水中速度是4m/s，
求（1）当小船船头始终正对岸时，它将在何时何处到达对岸？
（2）要使小船到达正对岸，应如何行使，经多长时间过河？
(a) (i) Explain whether Niamh can qualify for the home carers tax credit for the years 2008 and 2009; (3 marks)(ii) State the implications for Keith and Niamh if she claims this tax credit for 2009. (1 mark)Note: Computations are not required for part (a).
