单选题：Given the adjacency list of a directed graph,

Given the adjacency list of a directed graph,
```
a: e,f,g
b: Empty
c: Empty
d: b,c
e: Empty
f: d
g: c
```
which one below is NOT a valid topological order of the graph?
@[C](3)

A. `a, e, f, d, b, g, c`
B. `a, f, e, d, g, b, c`
C. `a, e, g, c, f, d, b`
D. `a, g, f, e, d, c, b`



A.`a, e, f, d, b, g, c`
B.`a, f, e, d, g, b, c`
C.`a, e, g, c, f, d, b`
D.`a, g, f, e, d, c, b`


答案：C