For which purpose is the command mpls ldp maxhops used?

A.
In large ATM-MPLS networks, the LFIB can become too large and it may be necessary to limit
the
maximum diameter of the MPLS LSPs.

B.
Because downstream-on-demand label allocation uses hop count to control loop detection, it
maybe
necessary to limit the maximum diameter of the MPLS network.

C.
Because end-to-end delay can cause problems with some voice applications, it may be
necessary to limit the maximum diameter of the MPLS network.

D.
When interconnecting large frame mode MPLS and cell mode networks it may be necessary to
limit the maximum network diameter to prevent forwarding loops.

Explanation:
You can set the max-hops parameter so that LDP will be “faster to”/”better at” finding a routing
loop. If you have a ring topology of 50 routers and all links are equal cost, you can define maxhops to 25 as the shortest path will always be less that 26 hops. (Except if you have a link down
somewhere. But this is a theoretical problem a you would never so large a ring topology.) if Max
hops hasn’t been configured ldp won’t know until after 50 hops.
In the explanation supplied with the wrong answer D it even says “This threshold is used to
prevent forwarding loops in the setting up of label paths across an ATM region” this further
supports that the right answer is B as Max-hops isn’t used with frame mode.
(frame mode uses the IGP for loop detection)