What term doesn't belong : gunpowder, calvary, fake retreat, psychological warfare

Calvary

Explanation:

I Think its Calvary because gunpowder, psychological warfare, and fake retreat are acts during war that can influence your enemy but the Calvary is a title of horsemen that charge into battle.

Gunpowder affects the mind after a while making you woozy during battle and you start to get headaches from it (especially during the 1800's nobody drank water really).

Psychological warfare can instill fear into the hearts of your enemy for instance Vlad the Impaler impaled over 1000 prisoners on the way to his fortress which instilled so much fear into the Ottoman army they turned back.

A fake retreat can make any enemy chase after you and if you have another army not too far away you can cut down the very tired imposing army.

B. It becomes a push factor.

Explanation:

In the mid-1800’s, a large number of immigrants crossed the Atlantic Ocean to begin a new life in America from Europe. More than 3 million of these immigrants arrived from Ireland and Germany. Many of them were fleeing economic or political troubles in their native countries.    

During this time period, technology was developing rapidly. The Industrial Revolution had begun. Larger faster steamships brought people to America by the thousands. Railroads grew and expanded. People could travel quickly and efficiently. Factories were built to produce many new products only recently invented.  

With the rise of American industry, growth of the railroad system created thousands of jobs both in factories and in the construction trade.

Hope this helps :)