The 12th Amendment was needed because...

To prevent deadlocks from keeping the nation leaderless.

Explanation:

The Twelfth Amendment provided that if the House did not choose a President before March 4 (then the first day of a Presidential term), the individual elected Vice President would "act as President, as in the case of the death or other constitutional disability.

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d) a constitutional amendment

first industrial revolution - the first wave of the industrial revolution lasted from the late 1700s to the mid-1800s. it industrialized the manufacture of textiles and began the move of production from homes to factories. steam power and the cotton gin played an important role in this period.