Correct Answer - Option 2 : During storms at least one road is open.
Given: Six roads : A, B, C, P, Q and R
i) Only one out of A, P and R is open at any one time.
A/P/R
ii) If B is closed, so is Q.
B (no) → Q (no)
iii) Only one of A and B is open during storms.
Storms : A /B
iv) P is closed during flood.
Floods : P(no)
1)Under normal conditions only three roads are open. → False (as it is possible but not definite)
2) During storms at least one road is open. → True (as either A or B is open during storm)
3) During floods only three roads are open. → False (as it is possible but not definite)
4) During calamities all roads are closed. → False (as either A or B is open during storms)
Hence, 'During storms at least one road is open.' is the correct answer.