Final answer:
A physical observation refers to something that can be directly observed or measured without changing the substance being observed.Option (b),'melts at 76C', is an example of a physical observation.
Step-by-step explanation:
A physical observation refers to something that can be directly observed or measured without changing the substance being observed. Option (b), 'melts at 76C', is an example of a physical observation because it describes a change in state (solid to liquid) at a specific temperature. The other options, (a) burns in oxygen temperature, (c) forms a white precipitate, (d) decomposes in air, and (e) cooks at high, describe chemical reactions or processes, which are not considered physical observations.