Question

fill in with appropriate preposition. The boy sat still-------the night waiting to be called

Answer 1

The boy sat still at the night waiting to be called

Answer 2

The most appropriate  preposition to be filled in the sentence is 'throughout'.

The meaning of 'throughout is 'during the whole period of something'.

So, the complete sentence should be written as shown below:

The boy sat still throughout the night waiting to be called.

The sentence means the boy kept sitting the entire night in hope to be called.