How do I tell the difference between a proper noun or a normal noun Jk who wanna be my gf or bf

Mexico city is an example of how humans alter their environment because it was a. one of the world’s largest cities b. built on drained and filled lake beds c. built after conquest by the spanish d. once the capital of the aztec empire

In which direction does the moving force of air flow? a-from warm temperatures to cold temperatures b-to areas of high pressure to areas of low pressure c-east to west d-from high elevations to low elevations

The ethnic conflicts in darfur have led to an attempt to destroy a whole people known as