Choose the correct alternative:

Hydrogen satisfies the conditions of an ideal fuel but cannot be used freely because:

1. It is expensive
2. It is highly inflammable, so storing and transporting hydrogen is risky.
3. It has a high calorific value
4. It burns with an explosion.

Statements 1,2,4 are valid reasons.

Hydrogen satisfies the conditions of an ideal fuel but cannot be used freely because it is expensive, and burns with an explosion. It is highly inflammable, so storing and transporting hydrogen is risky. A fuel that has a higher calorific value is always considered a good option so it cannot be a reason to not use hydrogen freely.