Which technology helped bring trench warfare to a stalemate? O machine guns
O air reconnaissance
O barbed wire
O mines

according to the website the answer is;

Explanation:

Tanks. Tanks were developed by the British Army as a mechanical solution to the trench warfare stalemate. They were first used on the Somme in September 1916, but they were mechanically unreliable and too few in number to secure a victory.

basic principles: federalism, separation of powers, checks and balances, judicial review, representative democracy, limited government, rule of law, individual rights and responsibilities, consent of the governed, majority rule, popular sovereignty, equal protection.

that would be the steamboat because none of the other things are forms of transportation