Laura wants to develop a model that shows how natural processes can suddenly change the earths surface. which of the following could she show in the model?

a. erosion of a sandy beach by storms

b. formation of a canyon by a river

c. craving of a valley by a glacier

d. weathering of rocks by wind

plz!

Afactory makes propeller drive shafts for ships. a quality assurance engineer at the factory needs to estimate the true mean length of the shafts. she randomly selects four drive shafts made at the factory, measures their lengths, and finds their sample mean to be 1000 mm. the lengths are known to follow a normal distribution whose standard deviation is 2 mm. calculate a 95% confidence interval for the true mean length of the shafts. input your answers for the margin of error, lower bound, and upper bound.