Answer: 5.0 kb
Step-by-step explanation:
A restriction enzyme creates a double stranded cut on a DNA molecule. It recognizes and cuts at a specific sequence of DNA depending on the type of restriction enzyme used. If the DNA sequence is long enough it is likely that the enzyme will cut at multiple places causing multiple DNA fragments.
Most of the time to answer this question you would add up the kb at which there are bands. Lane 1 is simply used as a measuring tool to give you a reference to the size of the DNA. The smallest size of uncut DNA in this case would be 5.0 kb. It is not a very good question considering the DNA sample would typically be homogeneous and there would be enough restriction enzymes to cut all the DNA at the sites but based off of the answer choices 5 kb is the minimum size that the DNA could possibly be if it had not been cut.