a. Unless it will rain. I will pick you up at 6.00.
b. If you don't pass the test, what will you do?
c. Take another sandwich if you are hungry.
Choose the correct sentence/s.

The correct answer is Option D (Only b and c).

Key Points:
• In conditional clauses introduced by 'if' or 'unless', the future modal 'will' is NOT used; the simple present tense must be used instead (e.g., 'Unless it rains...'). Moreover, sentence a erroneously puts a period (.) after 'rain'.
• Sentence b: 'If you don't pass the test, what will you do?' is a correct First Conditional sentence (If + present simple, will + V1).
• Sentence c: 'Take another sandwich if you are hungry.' is a correct Zero/Imperative Conditional sentence.
• Option 4 (Only b and c).
• Sentence a is incorrect both in tense ('will rain' instead of 'rains') and punctuation.
• Sentences b and c are completely correct.
• Key Takeaway: Conditional clauses with 'if' or 'unless' use the simple present, not 'will'; sentences b and c are correct.