Identify the correct statements among the following:
a. is used as a refrigerant for ice-cream and frozen food.
b. The structure of contains twelve six-carbon rings and twenty five-carbon rings.
c. ZSM-5, a type of zeolite, is used to convert alcohol into gasoline.
d. CO is a colourless and odourless gas
1. (a) and (c) only
2. (b) and (c) only
3. (c) and (d) only
4. (a), (b) and (c) only