Sometimes questions do not have to totally make sense to convey the proper message. In the examples shown the OP has correctly stated the rating of the service in terms of the information provided. Sometimes we want to equate theoretical questions with real life situations…ignore that aspect of the question and take the values at face value.
The OP is using the weakest link method of determination of the service based on given (assumed known) information. In the real world it wont be that simple and in some cases you will only have 2 or 3 of the key factors to rely on…but usually the signs are evident if you just look for them.
Now the questions - The answer to A is indeed 125A as that is the limiting factor. In the second example, it would appear that the meter base is the limiting factor. However, there are indeed (real world creeping in now) some meter enclosures that are 60A and/or 125A depending on the time frame and since the physical nature of the meter was not expressed…we have to assume they validated this fact.
Now…the bigger message here to an HI is this. If in example 2 you notice the situation it is fairly observant that either an unauthorized upgrade took place (based on the given example parameters) or someone is mistaken about the meter size and ratings. So with that said it would be customary to question that fact on your report.
However, if you are unclear on the meter (and at this point no physical attributes are given, so I may disregard it) I would not loose sleep over rating it a 100A with an explanation again of the meter situation. Either way you have conveyed the message to the customer that is needed in a truthful and accurate depiction.
Just my thoughts on the subject.