ASSERTION
Dilute HCl cannot be concentrated beyond a certain concentration by boiling.
REASON
HCl boiling and melting point depend on the concentration or molarity of HCl in aqueous solution. They range from a very low conc of 0% HCl to values for fuming HCl at over 40% HCl.
A. Both Assertion and Reason are correct and Reason is the correct explanation for assertion.
B. Both Assertion and Reason are correct and Reason is not the correct explanation for assertion.
C. Assertion is correct but reason is incorrect.
D. Both assertion and reason are incorrect.

Hint: The boiling point and the melting point of the solution is dependent on the number of moles of solute dissolved in the solution. As the boiling point increases the number of solutes particles in the solution increases.

Complete step by step answer:
The dilute HCl solution is formed by dissolving the HCl gas in water.
When the dilute HCl solution is heated at $20^\circ C$, the maximum concentration which is obtained is 39.1 %. In 39.1%, 39.1 g of HCl is dissolved in 100 g of water.
When the dilute HCl solution is heated at $110^\circ C$, the maximum concentration obtained of the HCl solution is 20 %. In 20 %, 20 g of HCl is present 100 g of water.
If the dilute HCl solution, having the concentration of 36.5 % is heated at $110^\circ C$, the HCl gas present in the solution will be evaporated and bye removed before the concentration of the solution reaches 20 %.
So, from the above details it is clear that the concentration of the solution is dependent on the boiling point of the solution.
Thus, both the assertion and reason are correct and the reason is the correct explanation of the assertion.

Therefore, the correct option is A.

Note: The maximum concentration of the dilute HCl solution which can be obtained is 40%. HCl is a very strong acid and is highly corrosive. Dilution of strong acid is an exothermic process as heat is released.