What could cause the symptoms?

The Testking network is shown below:

A technician is investigating a problem with the network shown above. These
symptoms have been observed:

1. All of the user hosts can access the Internet.
2. None of the user hosts can access the server in VLAN9
3. All of the hosts can ping each other.

A. Interface S0/0 on the router is down.
B. Interface Fa0/1 on the router is down.
C. Interface Fa0/5 on Testking3 is down.
D. Interface Fa0/4 on Testking3 is down.
E. Testking2 is turned off.
F. Trunking is not enabled on the link between Testking1 and Testking3.

Answer: D

Explanation:

Since all user hosts have access to internet, link to router has to be up. Therefore, router
interface (Fa0/1 - believe it is labeled incorrectly on diagram as Fa1/0) must be up. Since
all hosts can ping each other, but none can get to VLAN 9 which is through single
interface Fa0/4, this interface must be down.
Choice A: incorrect, S0/0 must be up if internet access available.
Choice B: incorrect, Fa0/1 must be up if internet access (through router) available.
Choice C: incorrect, would not prevent access to VLAN9 via other routes (i.e Fa0/7,
Fa0/9, Fa0/4)
Choice D: correct
Choice E: incorrect: TestKing2 must be up if internet access (through switch and then
router) available
Choice F: incorrect: Disabled trunking on link between TestKing1 and TestKing3 would
not prevent access to VLAN9 via other routes