a) When data is transformed, there is always a loss of information.
False, that depends on the type of transform; e.g. transformation of digital data may be lossless.

b) Each measurable metabolite/chemical compound has a characteristic spectrum.
Maybe. Chemical compounds that do not have atoms with a nuclear spin can't be distinguished using NMR (but works for MS)
True (measurable!!!)

c) From a spectrum of human urine, all compounds can be identified and quantified.
False. The spectra of all compounds overlap in the spectrum of the urine sample; Only the abundant ones can be distinguished...