C. gravitational force
Answer:
1) Hydrogen
2) Methane
3) Carbon
4) Structural isomer
5) Ethene also known as ethylene
6) Hydrocarbons are widely used as fuel
7) Crude oil
Explanation:
ⁿᵘ ᵗʰˣ ⁱᵐ ᵃ ᵍᵘʳˡ -.-