Answer:
A. the increase in the number of pounds a boy gains each year
Step-by-step explanation:
Any function that can be written as:
y = ax + b
is called a linear function.
Slope of the function (or sometimes referred to as "steepness") is determined by the value of a, which is 1.73 in our case. Since y is number of boy's pounds and x is his year, that means that for every year (when x changes by 1), the boy's weight (y) will change by 1.73.
Value of a is positive (1.73), which means that for each year, from this 5 to 18 interval, boy's weight will increase.