Final answer:
The number of DNA fragments obtained after cutting circular DNA with restriction enzymes XhoI and SmaI depends on the number of recognition sites present. Without a figure to specify the sites, an exact answer cannot be given, but multiple sites would lead to multiple fragments.
Step-by-step explanation:
If you cut a piece of circular DNA with the restriction enzymes XhoI and SmaI, the number of DNA fragments produced will depend on the number of recognition sites for each enzyme on the DNA molecule. Each enzyme has a specific recognition sequence at which it can cleave the DNA. After the DNA is cut, fragments can be separated and analyzed using agarose gel electrophoresis. When running a gel, if you obtain more than one band, this indicates that multiple fragments have been produced. As there is no figure provided to determine the exact number of recognition sites for XhoI and SmaI on the circular DNA, a generic answer cannot be given. However, in general, if each enzyme has a single recognition site, cutting with both would result in two DNA fragments. If there are more recognition sites, there will be correspondingly more fragments. Therefore, without specific information, the answer could be none of the above because the number of fragments depends on the number of recognition sites present.