Final answer:
The Salem-Sump and Levin tubes are examples of nasogastric tubes, while the Swan-Ganz is not. Therefore, the correct answer to the student's question is B. 2 only.
Step-by-step explanation:
The student's question pertains to types of nasogastric (NG) tubes which are used for medical purposes. Specifically, the student is asking to identify which of the listed options are examples of NG tubes. The examples provided are the Swan-Ganz, Salem-Sump, and Levin tubes. The Swan-Ganz catheter is not a nasogastric tube, but rather a special type of catheter placed into the pulmonary artery. It is used for measuring pressures in the heart and lungs. On the other hand, both Salem-Sump and Levin tubes are indeed types of nasogastric tubes designed for gastrointestinal decompression and enteral feeding. Therefore, the correct answer is B. 2 only, indicating that only the Salem-Sump tube is an example of an NG tube.