Which field in the MPLS shim header is used to support different QoS markings?

Which field in the MPLS shim header is used to support different QoS markings?

A.
IP precedence

B.
DSCP

C.
EXP

D.
ToS

E.
S

F.
Label

Explanation:

MPLS EXP Marking
The three MPLS EXP (experimental) bits in the shim header of an input or output MPLS packet
header may beset or changed by a user configured value