Tom begins a hike at an elevation of 6,000 feet. Toms elevation at any time is shown on the graph below which steam is true ?
A. The elevation Tom is not always decreases compared to the time
B. Tom decreases in elevation buy the same amount every hour for the last three hours
C. Tom walks at all times, for the entire hike
D. Tom never changes more than 1000 feet of elevation per hour