The correct answer is A) Before he left Maryland, he learned the blacksmith trade.
The sentence that contains consistency in verb tense is "Before he left Maryland, he learned the blacksmith trade.
When writing any sentence is very important to maintain the proper consistency of the verb tense. This means that the writer must keep the same tense in the sentence or clause. It is not good writing to have one verb in one form and another verb that is written in another form in the same sentence. There has to be the same period of time in the clause.