Pseudo First Rate Reactions

Trying to get some work done but this question has stumped me, because it isn't in my lecturer's notes (Despite it being referenced several times >:C):

When is it useful to define a "pseudo rate constant"?
>When all but one reactant is present in huge excess
>When the reaction shows an order that is not a whole number
>When one reactant is present in huge excess
>When the order of the reaction is not known.

It's multiple choice to make things more complicated. I thought the answer was >When all but one... and >When the order... but apparently I'm mistaken. Any ideas?

Reply 1

Nyctokinesis

I've realised one of my mistakes, it's >When one reactant... instead of >When all but one..., but I'm still unsure about the others. It's not >When the reaction shows an order that is not a whole number, because orders don't have to be integers but I don't know whether or not to choose >When the order of reaction is not known as well :/

Reply 2

Nyctokinesis

Having submitted my answer, I can confirm for any who might be interested that is wasn't >When one reactant is present in huge excess
and
>When the order of the reaction is not known.