Question

as soon as the bell rang the children ran out. No sooner.....

Answer 1

No sooner had the bell rung than the children ran out.

Answer 2

Answer:

No sooner had the bell rung, than the children ran out  

Explanation:

When using the phrase no sooner, it should be accompanied with than; this is to indicate that something was happening precisely the "same time" as another. The "formation" of these sentences is usually based on time frames, and it often incorporates the use of past tense. The perfect tense is commonly used in this type of sentences, but the past tense does not apply. Therefore the sentence above fits the words correctly forming a complete sentence.