The following output occurs on Router R1. IP SLA operation 1 uses an ICMP echo operation type, with default frequency of 60 seconds. The operation pings from address 1.1.1.1 to address 2.2.2.2. Which of the following answers is true reg arding IP SLA and object tracking on R1?（） R1# show track Track 2 IP SLA 1 state State is Up 3 changes, last change 00:00:03 Delay up 45 secs, down 55 secs Latest operation return code: OK Latest RTT (millisecs) 6 Tracked by: STATIC - IP - ROUTING 0

• A、The tracking return code fails after the SLA operation results in an ICMP echo failure three times.
• B、The tracking return code fails after the SLA operation results in an ICMP echo failure one time.
• C、After the tracking object fails, the tracking o bject moves back to an up state 45 seconds later in all cases.
• D、After moving to a down state, the tracking object moves back to an OK state 45 seconds after the SLA operation moves to an OK state.