Which statement is true about this D script?

Examine the D script: syscall::write:entry {
@[execname] = avg(arg2);
}
Note that the third argument to the write(2) system call is the size of the write being made. Which statement is true about this D script?

A.
it displays the average write size that each unique process makes.

B.
it displays the average write size that each running program makes.

C.
it does not run because the aggregate is not named.

D.
it runs but produces no output.