No, the answer is b. First Golden Rule of Heroclix:

Kind of curious why you think it is a.

Although, calculating the range for Puise Wave specifically did work differently in the 2014 Rules so I see where it might be confusing if you remember how it worked before.

Prior to it being omitted from the rule book, Area of Effect had to be determined when using Pulse Wave, and since "replace then modify" only applies to combat values - and Area of Effect is not a combat value - the way Pulse Wave's "range" was determined was 'a'. Was there a recent change in the rules that I've not been made privy to?

Also...

Pulse Wave begins with "Halve range". Wouldn't that mean determining range before halving? So apply modifiers before halving? Also remembering that Pulse Wave's "range" is not a combat value (it is determined by range which is a combat value, but not a combat value itself).

Areas of effect don't exist anymore. It used to work this way pre-2017 Rules, but does not any longer. You now calculate the range for Pulse Wave the same as any other time you would calculate range: Printed then Replace then Modify (then Minimums/Maximums.)

No. That is the standard way powers are written now. Look at Charge, Running Shot and Hypersonic Speed for example. Pulse Wave's range is calculated just like any other combat value.