To solve this problem, we need to arrange the steps in the formation of recombinant DNA in the correct sequence. Let's analyze each step:$\newline \bullet$C. Isolation of desired DNA fragment:$\newline$ - The first step in forming recombinant DNA is to isolate the DNA fragment that contains the gene of interest.$\newline \bullet$B. Cutting of DNA at specific location by restriction enzyme:$\newline$ - Once the desired DNA fragment is isolated, restriction enzymes are used to cut the DNA at specific sites to facilitate the insertion of the gene of interest.$\newline \bullet$D. Amplification of gene of interest using PCR:$\newline$ - After cutting, the gene of interest is often amplified using Polymerase Chain Reaction (PCR) to produce multiple copies for further manipulation.$\newline \bullet$A. Insertion of recombinant DNA into the host cell:$\newline$ - Finally, the amplified recombinant DNA is inserted into a host cell for expression or cloning.$\newline$Now, let's arrange the steps in the correct sequence:$\newline C \rightarrow B \rightarrow D \rightarrow A \newline$This corresponds to Option 3: C, B, D, A.