The blank requires a noun at its place as the definite article 'the' requires a noun after it. The sentence talks of electric grids, cars and telephone making the lives easier for people. The word 'invention' (the action of inventing something, typically a process or device) fits correctly in the blank as its use conveys that the innovation of electric grids, etc. in the 1900s made lives easier. Hence, option (b) is the correct answer.
The word 'formulate' is a verb while the word 'creative' is an adjective, but the blank requires a noun. Hence, options (a) & (d) are eliminated. The words 'story' and 'originality' are irrelevant to the context of the sentence and their use in the sentence renders it meaningless. Hence, options (c) & (e) are eliminated.
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