In the sentence "Haris mowed the lawn and he earned a hundred rupees," the word "and" is Option 3: a Coordinating conjunction.
Coordinating conjunctions are used to connect words, phrases, or independent clauses of equal importance. In this sentence, "and" is used to connect the two independent clauses "Haris mowed the lawn" and "he earned a hundred rupees." It joins these two clauses together to show a relationship of addition or continuation.