Why do black holes exist and why do neutron stars exist? i can't seem to find anything online explaining why they might actually exist

Complete the activity titled "comparative urban environments." every city is shaped by different cultural forces. in one to two paragraphs, contrast the culture of two different cities from this activity: new york and buenos aires. what makes these cities stand apart from each other culturally? what is unique about each city’s attitude, language, habits, foods, or architecture?

Witch of the following types of boundaries is most likely to result in a subduction zone

Monk's mound in cahokia is an enormous earthwork very near to the mississippi river. what do archaeologists believe it was used for?