How do any of the answers have anything to do with the question? Unless we see the import/export route target on the remote PE, any of these answers could be right.

Since VRF customer_a is exporting and importing with a Route Target of 1:1, the remote device must also be exporting and importing with a Route Target of 1:1. So, the answer is D.

A or D is the answer, but it is unclear whether this Config is on the network administrator's side or the remote technician's side.

A, B, and C it is exporting the wrong route target. It needs to export 1:1, or the customer_a site can't import it. The RD doesn't matter.

Rt can be same on both routers, correct answet

Without seeing the configs on the other side of the router, it is impossible to decide what should be configured on CE router

The route-target at remote site connot export route-target 1:2 only, because our router imports route-target 1:1. the remote site MUST export 1:1 (and others if it desires)

What's the difference between : route-target export 1:1 route-target import 1:1 VS route-target both 1:1 From what I know these are the same, with the latter just being a shortcut for writing it. source: https://summalai.com/?p=2980 so how is this the answer?

is D: The network administrator configured VRF lite for customer A. The technician at the remote site misconfigured VRF on the router. Which configuration will resolve connectivity for both sites of customer_a?

For basic VRF-lite there is no need to specify RD or export import targets. So the question is missing context. It seems they do some kind of route leaking and require this at both ends. Just reading the question again, you should assume there is a requirement of route leaking with MP-BGP. Not sure, but personally this is far more complex than basic VRF-lite.

As Masashi_O is saying, if we were doing some leaking we would not use the import and export route target as both; in this case they just want to let the same VRF talk using MPLS. Even if the RD is 1:2 it does not matter, what makes things work is the route target, the route-target makes the decision to receive something or send something. The RD just identify the VRF of the prefix

The question is fine. If you assume we are configuring to Site A routers, and our router in the config had route-target import 1:1 route-target export 1:1 the only way the two site A routers import/export prefixes is through the same route-targets. D is the only possible answer when configured on the technician remote site router.