Supply the missing word from these in the brackets:
- The material needs to prepare solar cell _____ [silicon/ sodium]
- Biogas contains mainly _____ [CH4/C2H5]
- The calorific value of methane is _____ KJ/g. [55/100]
- Carbon black is prepared from _____ [methane/coal]
- The material need to prepare solar cells is silicon.
- Biogas contains mainly CH4.
- The calorific value of methane is 55 KJ/g.
- Carbon black is prepared from Coal.