Which of the following words is NOT a valid synonym (Paryayvachi) of the term 'अमृत'?

Let's look at the meanings of the terms:
* सोम, अमिय, and सुधा are well-established synonyms for 'अमृत' (Nectar/Amrit).
* On the other hand, the word क्षीर translates specifically to milk ($\text{दूध}$) or rice-pudding (kheer), and is not semantically associated with nectar.