Identify the correct statements among the following:

a. ${\mathrm{CO}}_2\left(\mathrm{g}\right)$ is used as a refrigerant for ice-cream and frozen food.

b. The structure of ${\mathrm{C}}_{60}$ 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