Answer is: <span>a. two 511 kEv photons are formed. </span><span>When the positrons reach thermal energies, they start to interact with electrons by annihilation.</span> Positron-emission tomography<span> (</span>PET)<span> is a </span>nuclear medicine functional imaging<span> technique that is used to observe metabolic processes in the body. The system detects pairs of </span>gamma rays<span> emitted indirectly by a </span>positron<span>-emitting </span>radionuclide.
And, water is called the "universal solvent" because it dissolves more substances than any other liquid. This allows the water molecule to become attracted to many other different types of molecules.
