Air pollution in us and canadian cities is caused mostly by a. clear-cutting forests for timber b. releasing emissions from vehicles and industry c. dumping runoff from farms into rivers d. harvesting minerals from mines

Most air pollution in United States and Canadian cities is caused by vehicle and industrial emissions. The correct option among all the options that are given in the question is the fourth option or option "D". This has led to increased amount of global warming. I hope the answer has helped you.

here are some major conflicts i found. maybe pick one and do more research on it. (cause i ain't writing 6 paragraphs)

in 1877, the nez perce war took place.

1881 - president james garfield was assassinated.

1882 - the chinese exclusion act was passed.

1883 - a decision in the civil rights cases legalized racial segregation in the united states.

1887 - the dawes act was passed.

1893 - the panic of 1893 took place. (what a creative name)

and there are probably other topics you can find if you just search up "united states timeline," or "conflicts in the 19th century for america."

then once you find a topic you like find out how it affected the people of america and what not. (sorry if this feels a bit short changed, history was and never will be one of my strong topics)