单项选择题
Questions 17-20 Match the toxic gas in the box to the effects below. Choose your answers from the box and write the letters A-D next to questions 17-20. Toxic gases
It hurts the lungs.（）
A．carbon dioxide B．nitrogen oxide C．carbon monoxide D．hydrogen sulphide
判断题 The full cost of the tour must be paid at the time the booking is made.（）
单项选择题 5ZBG primarily（）
单项选择题 A creative response—be inventive______
