A/an is a mass of undissolved matter that is present in and transported by the blood.
a. embolus
b. aneurysm
c. false aneurysm
d. thrombus

your answer is "the 1950's"

weathering - colorado river carves land in arizona to form the grand canyon. cracks form in a sandstone wall surrounding a house. a marble statue near the science museum is changing color due to rainfall

erosion - after a rainstorm, soil and rock piees litter the roadways. the sand dunes in the sahara desert are changing shape.

here's your answer.