Final answer:
The correct phrase to complete the sentence is 'pains,' which means the speaker took great care to ensure no blame was placed on the others involved. Option A is the correct answer.
Step-by-step explanation:
The phrase you are referring to is often used to communicate that the speaker was trying hard to ensure that no blame was being placed on the parties they were addressing.
In English, certain expressions are colloquially used to denote that one has taken great care to avoid a specific outcome. In this case, the most suitable option to complete the sentence "I was at... to make it clear that I wasn't blaming on them." would be 'pains', as the term refers to taking care to do something with a lot of effort or diligence.
Therefore, the correct option to complete the sentence would be:
a. Pains