posted by Callie .
Avalanches are caused by a variety of conditions. When the temperature is cold and snow falls, the snowsticks to the ground. However, when the air temperature changes, the snow may slide away in pieces or slabs. Basically an avalanch happens when the gravity of snow heading downhill is greater than the gravity holds the snow together on the ground. Steep slopes on mountains, a recent heavy snowfall, a weak layer in the snow cover, changes in the weather, and changes in pressure on the suface (such as a skiers's sudden weight) can all contribute to the creation of an avalanch.
Avalanches, happen in a series of stages. First, while the temperature is cold and there is a heavy snowfall, the snow will stick to the ground. Suppose that what happens next is that the air temperature changes after the snow has fallen. Then, a layer of snow may weaken. Next, suppose that a skier lands on the weakend snow. The snow may then slide away from the ground in pieces or slaps. As the slaps head downhill, their gravity is greater than the snow underneath. They may slide down a steep slope, creating a major avalanche.
According to Passage B, which phrase describes the first stage of an avalanche?
A. The slabs head downhill
B. The temperature is cold
C. The air temperature changes
D. A layer of the snow may weaken
Is the answer d?