Answer:
3. After
Step-by-step explanation:
The best suitable word to be inserted into the blank (A) is "After".
The word 'after' can be used as a preposition, adverb and a conjunction. 'After' can be used as a preposition when it is followed by a noun in the sentence.
In the context, the word "after" is the best suitable word and it is used as a preposition as it is followed by the word 'approval' which is a noun.