Answer:
Option B: 
Step-by-step explanation:
A function is said to be increasing if it has a slope greater than 0.
The function with the largest slope has the highest increasing rate.
Here, for the graph in option A, the function is decreasing with increasing
. So, it has a negative slope.
We need to convert equation of option B into standard form and then determine its slope.
The standard form of a straight line is
, where
is the slope of the line and
is the y-intercept.
Now, given function is:

Therefore, the slope is 2.
Option C:
Slope is given as,

Therefore, the slope is 1.
Option D:
Equation of a line with
and
as
and
intercepts is given as,

Here,
and 
∴ 
Therefore, the slope is
.
Hence, the largest slope is for option B and thereby the highest increasing rate.