I cannot see underlined words in the sentence from your question but I can tell that it is about the word ''so'' because this is an example of conjunction that is connected to the beginning of the sentence with ''We closed the shop''.
There is no proposition or interjection in this sentence so those two are incorrect answers.
Conjunction is often used in the sentences to connect and coordinate clauses and sentences so they can be more meaningful. Some other examples of conjunction are: For, And, Nor, Such...that, and more.
it is so much important to be deliberate and discipline in our relationship to technology as if we don't become serious about them it would may lead to its disadvantage and have negative effect to our life
