To solve this problem, we need to analyze the given statements:$\newline$Assertion (A): Polymerase chain reaction is used in DNA amplification.$\newline$Reason (R): The ampicillin resistant gene is used as a selectable marker to check transformation.$\newline$Let's break down each statement:$\newline \bullet$Assertion (A):$\newline$ - The polymerase chain reaction (PCR) is a technique used to amplify specific DNA sequences.$\newline$ - It allows for the rapid and exponential increase of a particular DNA segment.$\newline$ - Hence, Assertion (A) is correct.$\newline \bullet$Reason (R):$\newline$ - The ampicillin resistant gene is commonly used as a selectable marker in genetic engineering.$\newline$ - It helps identify cells that have successfully incorporated foreign DNA by providing resistance to the antibiotic ampicillin.$\newline$ - Hence, Reason (R) is correct.$\newline$Now, let's determine if (R) is the correct explanation of (A):$\newline \bullet$While both statements are correct, the reason does not explain the process of DNA amplification.$\newline \bullet$PCR is a method for amplifying DNA, whereas the ampicillin resistant gene is related to selecting transformed cells.$\newline$Therefore, (R) is not the correct explanation of (A).$\newline$Thus, the most appropriate answer is Option 2: Both (A) and (R) are correct but (R) is not the correct explanation of (A).