Answer:
e. To create valleys, glaciers have to be constantly advancing.
Explanation:
Although glaciers look like massive, solid blocks of ice, they actually move in a very slow manner, which is difficult to detect by the naked eye. The pressure that the glacier receives from the weight of the ice causes it to deform. As these changes occur, the melt water at the bottom of the glacier allows it to slide. It is this movement that allows for the formation of glaciers, as glaciers have to be constantly advancing in order to form valleys.
Answer: 
Explanation:
The Tropic of Cancer is one of the parallels (imaginary line around the Earth parallel to the equator) located in the northern hemisphere (currently its latitude is
).
It is called "Cancer" because a long time ago, when the summer solstice occurred in the northern hemisphere (on June 20th or 21st), the Sun was in the constellation Cancer (the crab).
Now, if we were just in the North Pole, Polaris would by exactly over our heads (
over the horizon), but as we go south and find the Tropic of Cancer parallel, Polaris altitude will be approximately at an angle of
over the horizon.
Hence, the altitude of Polaris measured by an observer at the Tropic of Cancer is
.