Final answer:
The mobile phase for an HPLC-UV experiment is typically a mixture of methanol and KH₂PO buffer solution; options provided by the student don't match this description.
Step-by-step explanation:
The mobile phase that will be used in this experiment is not explicitly listed among the options provided (krypton, toluene, acetonitrile, acetone, diethyl ether). However, if this is related to an HPLC-UV experiment described in the information provided, the mobile phase would typically consist of a mixture mentioned in the HPLC method: a mixture (25:75) of methanol and KH₂PO buffer solution. Neither of the options listed by the student appears in this description. It is possible that the intended experiment was not clearly described, and the student may need to refer to the specific method they're using to identify the appropriate mobile phase.