Match the column I & II using the code given below the column.
| Column I | Column II |
| A. Gas mask | 1. demineralise water |
| B. Permutit | 2. petroleum refining |
| C. Ion exchange resins | 3. softening of hard water |
| D. Silica gel | 4. Charcoal gas |
| | A | B | C | D |
| (a) | 4 | 3 | 1 | 2 |
| (b) | 3 | 4 | 2 | 1 |
| (c) | 1 | 2 | 3 | 4 |
| (d) | 2 | 1 | 4 | 3 |