This sentence can be rewritten using ‘No sooner’ as:
As soon as the siren blew, the firemen dashed towards their vehicle.

Correct option is C

The correct answer is option (c) No sooner did the siren blow than the firemen dashed towards their vehicle.
The expression "No sooner" is used for events that happen in immediate succession. When using it at the beginning of a sentence, it requires inversion—placing the auxiliary verb "did" before the subject. Also, it is followed by “than,” not “when.”
Explanation (Hindi):
जब “No sooner” का प्रयोग वाक्य की शुरुआत में किया जाता है, तो inversion का नियम लागू होता है यानी helping verb (did) पहले आता है। साथ ही, इसके बाद “than” का प्रयोग होता है, न कि “when”।
Grammatical rule used: No sooner + auxiliary verb + subject + base verb + than + second clause
Example: No sooner did I reach the station than the train left.
Meanings of all the other options:
· (a) – Incorrect: lacks inversion (no “did”).
Hindi: inversion नियम का पालन नहीं किया गया।
· (b) – Incorrect: again lacks inversion structure.
· (d) – Incorrect: wrong placement of “than,” violates standard structure.