Which test can quickly identify the core link that is causing the problem?

A service provider NOC engineer received numerous support tickets from their VPN customer. This customer are reporting packet loss between two PE routers. The NOC engineer created a VRF TEMP to run test between these two PE router and no error were reported. ECMP links are used between P and PE routers.

Which test can quickly identify the core link that is causing the problem?
A . an MPLS traceroute with multipath option between the PE`s loopback
B . an extended traceroute with multipath option between PE`s loopback
C . a VRF traceroute between customers1s CE router and service provider remote PE router
D . a VRF ping between customer`s CE router and service provider remote PE router
E . an extended ping with sweep option between the PE`s Loopbacks
F . an MPLS ping with sweep option between the PE`s Loopbacks

Answer: A