Final answer:
The correct fill-in for the sentence is 'would be,' which is part of the second conditional often used for hypothetical situations. It expresses a wish for more polite customers, which is not the current situation.
option 'b' is the correct
Step-by-step explanation:
The correct answer to the question If only customers _______ more polite, says the barista. is b) would be. This sentence construction utilizes the second conditional, which is used to talk about hypothetical situations and their consequences. In English, the second conditional is often formed using the structure 'if' + past simple, would + base verb.
Here, 'would be' implies a hypothetical situation in which the customers are more polite. The structure following 'if' should be in the past simple tense, which in this case, is implied through the use of 'would be'.
An example of how this could be used in a full sentence is: If only customers would be more polite, the atmosphere in the cafe would be much more pleasant. This expresses a wish or desire for a situation that is not currently true. It's important to note that in hypothetical conditionals, 'would' is used to talk about the desired or imagined outcome.