Consider the following statements regarding the fluidized bed combustion boilers:
1. The combustion temperatures are low, around 900°C
2. The formation of oxides of nitrogen is low.
3. It removes sulphur from coal during combustion process.
4. It requires high quality of coal as fuel.
Which of these statements are correct?
a. 1, 2, 3 and 4 b. 1,2 and 3
c. 2, 3 and 4 d. 1 and 4