Read the text and answer the question.
Avalanches are fast-moving masses of snow that slide down mountains. They can reach speeds of up to 80 miles per hour. Most avalanches happen during or after heavy snowfall, especially on steep slopes. Skiers and climbers should always check the weather forecast before going to mountainous areas.
Which of the following is **NOT** mentioned in the text?
A)The speed of avalanches
B)When avalanches usually occur
C)How to survive an avalanche
D)Who should be careful about avalanches