Supply the missing word from these in the brackets

Question

Supply the missing word from these in the brackets:

1. The material needs to prepare solar cell _____ [silicon/ sodium]
2. Biogas contains mainly _____ [CH4/C2H5]
3. The calorific value of methane is _____ KJ/g. [55/100]
4. Carbon black is prepared from _____ [methane/coal]

Answer

1. The material need to prepare solar cells is silicon.
2. Biogas contains mainly CH4.
3. The calorific value of methane is 55 KJ/g.
4. Carbon black is prepared from Coal.