Solar energy will not run out (unless the sun burns out), but the supply of fossil fuels we use is slowly depleting. Burning fossil fuel also releases greenhouse gas into the air, which is bad for the atmosphere.
Answer: 
represents oxidation.
Explanation:
Oxidation-reduction reaction or redox reaction is defined as the reaction in which oxidation and reduction reactions occur simultaneously.
Oxidation reaction is defined as the reaction in which a substance looses its electrons. The oxidation state of the substance increases.
Example:
Reduction reaction is defined as the reaction in which a substance gains electrons. The oxidation state of the substance gets reduced.
Example: 
represents oxidation.
Answer:
A. Both freezing and melting are physical changes.
Explanation:
Even if you were to freeze water, the molecules are still water molecules, and vise versa with melting it.
Step 1: Write the unbalanced equation,
C₂H₆ + O₂ → CO₂ + H₂<span>O
There are 2 C at left hand side and 1 carbon at right hand side. So, multiply CO</span>₂ by 2 to balance C atoms at both side. So,
C₂H₆ + O₂ → 2 CO₂ + H₂O
Now, count number of H atoms at both sides. There are 6 H atoms at left hand side and 2 at right hand side. Multiply H₂O by 3 to balance H atoms.
C₂H₆ + O₂ → 2 CO₂ + 3 H₂O
At last, balance O atoms. There are 2 O atoms at left hand side and 3 O atoms at right hand side. Multiply O₂ with 1.5 (i.e. 3/2) to balance O atoms. i.e.
C₂H₆ + 3/2 O₂ → 2 CO₂ + 3 H₂O
Hence, the equation is balanced. If you want to make equation fraction free then multiply all equation with 2. i.e.
( C₂H₆ + 3/2 O₂ → 2 CO₂ + 3 H₂O ) × 2
2 C₂H₆ + 3 O₂ → 4 CO₂ + 6 H₂O
