点燃笑气-乙炔焰前，一定要先点燃（）作为过渡。
参考答案：空气-乙炔焰
请问，北宋四大家是指黄庭坚、欧阳修、苏轼和（）？
In relation to employment law, discuss the common law duties of an employee under a contract of employment. (10 marks)
