Forms when updrafts and downdrafts within a cloud vertically move a particle of ice up and down, which allows a buildup of layers to occur on the ice until it bcomes to large to raemain aloft

d. new methods of assembly are introduced.

explanation:

this allows for the goods to be made on a larger scale. not faster because now it is shown to be made better, hence the greater productivity in the question. it is calling for something new to be introduced.

a characteristic is a deep cut in the earth or left over rock aka till.  

answer at the divergent plate boundary in the middle of the ocean;