Which two possible solutions can be implemented to avoid this situation in the future?

Refer to the exhibit.

A small enterprise connects its office to two ISPs, using separate T1 links. A static route is used
for the default route, pointing to both interfaces with a different administrative distance, so that one
of the default routes is preferred.
Recently the primary link has been upgraded to a new 10 Mb/s Ethernet link.
After a few weeks, they experienced a failure. The link did not pass traffic, but the primary static
route remained active. They lost their Internet connectivity, even though the backup link was
operating.
Which two possible solutions can be implemented to avoid this situation in the future? (Choose
two.)

A.
Implement HSRP link tracking on the branch router R1.

B.
Use a track object with an IP SLA probe for the static route on R1.

C.
Track the link state of the Ethernet link using a track object on R1.

D.
Use a routing protocol between R1 and the upstream ISP.

Explanation:
Interface Tracking
Interface tracking allows you to specify another interface on the router for the HSRP process to
monitor in order to alter the HSRP priority for a given group.
If the specified interface’s line protocol goes down, the HSRP priority of this router is reduced,
allowing another HSRP router with higher priority can become active (if it has preemption

enabled).
To configure HSRP interface tracking, use the standby [group] track interface [priority] command.
When multiple tracked interfaces are down, the priority is reduced by a cumulative amount. If you
explicitly set the decrement value, then the value is decreased by that amount if that interface is
down, and decrements are cumulative. If you do not set an explicit decrement value, then the
value is decreased by 10 for each interface that goes down, and decrements are cumulative.
The following example uses the following configuration, with the default decrement value of 10.
Note: When an HSRP group number is not specified, the default group number is group 0.
interface ethernet0
ip address 10.1.1.1 255.255.255.0
standby ip 10.1.1.3
standby priority 110
standby track serial0
standby track serial1
The HSRP behavior with this configuration is:
0 interfaces down = no decrease (priority is 110)
1 interface down = decrease by 10 (priority becomes100)
2 interfaces down = decrease by 10 (priority becomes 90)

http://www.cisco.com/en/US/tech/tk648/tk362/technologies_tech_note09186a0080094a91.shtml#i
ntracking