This question tests your understanding of verb tenses and voice in conditional sentences. Let's analyze the structure:

The sentence begins with "If there is fuel shortage," which is a conditional clause referring to a possible future situation. The main clause should logically follow with a consequence of that condition.

Now let's examine the options:

Option 1: "Had to be developed" - This uses past tense, which doesn't match the future condition.

Option 2: "Has to develop" - This is present tense and active voice, suggesting solar energy is developing something itself, which doesn't make logical sense.

Option 3: "Will have to be developed" - This is correct! It uses future tense ("will") and passive voice ("be developed"), indicating that solar energy will need to be developed by someone in response to the fuel shortage.

Option 4: "Will have to develop" - This uses future tense but active voice, again suggesting solar energy will develop something, which is illogical.

The correct answer is: Will have to be developed

Related Concepts

Conditional Sentences: When we talk about possible future situations using "if" clauses, the main clause often uses future tense to show the consequence.

Passive Voice: We use passive voice (be + past participle) when the subject receives the action rather than performs it. Solar energy doesn't develop itself - people develop solar energy.

Modal Verbs: "Will have to" expresses future necessity or obligation.

Key Formula

Future Conditional Structure: If + present tense, will + base verb

Passive Voice Formula: Subject + will + be + past participle