If you look at a square made up of alternating red and blue stripes for several minutes and then look immediately at a blank white sheet of paper, you will see a square with alternating green and yellow stripes. This effect results from pairs of that work .

this is a pretty broad question and can be a pretty lengthy answer. since 1900, women have gained a lot more rights and have become active in the workforce. with women being in the workforce, men play a larger role in family life. many family tasks are shared between men and women, whereas, women used to be the sole family caretakers.

that should get you started at least.

b. the american revolution