While a user is compiling a C program, "vmstat 120 10" is run to determine the cause of a performance problem.  Using the vmstat output as shown in the exhibit, which of the following conclusions is most appropriate to draw?（）

• A、 There is a file I/O bottleneck.
• B、 There are too many open files. 
• C、 There appears to be a buffer shortage. 
• D、 There is a paging space I/O bottleneck.