The o horizon is a dense layer of fine soil and clay. true or false

What evidence does the writer give to support his argument about coral reefs? a) he speaks of the activities of coral polyps. b) he describes the composition of the great barrier reef. c) he emphasizes the ways in which coral reefs are fragile. d) he points out the ways that scientists do research on the reefs.

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

All material in the universe that has mass and occupies space is called