Consider the following processes:
1. Gas welding
2. Thermit welding
3. Arc welding
4. Resistance welding.
The correct sequence of these processes in increasing order of their welding temperature is
(a) 1, 3, 4, 2 (b) 1, 2, 3, 4
(c) 4, 3, 1, 2 (d) 4, 1, 3, 2