An iso-profit line represents
 \[A.\] An infinite number of solutions all of which yield the same profit.
\[B.\] An infinite number of solutions all of which yield the same cost.
\[C.\] An infinite number of optimal solutions.
\[D.\] A boundary if feasible region

Hint: First of all, we should analyse the given word. We should divide the word “iso-profit” into two parts. Now we should understand the meaning of each part. Now, we should obtain a final statement based on the above explanation. Now we will compare it with given options and we will find the correct option.

Complete step-by-step answer:
Before solving the question, we should analyse the word “iso-profit line”. The word “iso-profit” can be divided into two parts. Let us assume the first part as “iso” and let us assume the second part as “profit”. We know that the word “iso” represents “same”. The word “profit” represents “profit”. So, the word “iso-profit” represents “same profit”.

So, it is clear that the word “iso-profit” represents “same profit”. In the question, it is mentioned about the “iso-profit line”. We know that a line is said to be extended up to infinity. So, the line will have infinite solutions.
So, we can say that the profit is constant in an iso profit line.

So, the correct answer is “Option A”.

Note: Students have a misconception that option B may be correct. We know that if the difference of measured price to cost price is positive, then this difference is said to be profit. From the iso-profit line, it is clear that the profit is constant. If the difference between a and b is constant then we cannot say that a and b are constant. Let us assume the profit as p. If we assume cost price as x and selling price as y, where profit p is constant, then the line equation obtained is \[y-x=p\].
Hence, option A is only correct.