Multiple-choice questions Section A Choose the most suitable answer and write the corresponding letter (A, B, C or D) in the brackets provided. 1. Which of the following is not true about air? (A) Air is a mixture, (B) The density of air is less than the densities of its gaseous components (C) Air supports burning. (D) The gases in air can be separated by physical methods. 2. Which statement about carbon dioxide gas is true? (A) It is produced when plants photosynthesise. (B) It is used in rocket fuels. (C) It relights a glowing splint. (D) It is produced when wood is burned.