The limitations of the source identified by the writer include:
- **The omission of important details**: The writer points out that critical information, such as the length of delays in decisions and the number of alumni surveyed, is missing from the graph. This omission can impact the accuracy and completeness of the conclusions drawn from the data presented.
The other options mentioned are not explicitly identified as limitations in the statement provided. However, they could also be potential limitations depending on the context of the source and the analysis being conducted.