Answer:
 interval B is the answer.
Step-by-step explanation:
We have given a graph.
We have to choose the interval where the function is linear increasing.
From graph,
In interval A, Function is linear decreasing.
In interval B,since at x  = 2 ,y  = 4 and at x = 4, y = 6
 Function is linear increasing.
In interval C , function is constant.
In interval D , function is linear decreasing.
Hence, interval B is the answer.