Each of the following sentences has a blank space and four words given after it. Select the word which consider most appropriate for the blank space and indicate your choice.
'Please' and 'Thank you' are the little courtesies by which we keep the __________ of life oiled and running smoothly.
Option B is the right answer.
“A well oiled machine” is a phrased used to refer to something that runs smoothly and without problems. Source: https://www.macmillandictionary.com/dictionary/british/well-oiled