The diagram below shows some subatomic particles.

which of these statements best identifies the particle that is labeled with an x?
it is either an electron or an isotope.
it is either a proton or a neutron.
it is either a beta particle or a nucleus.
it is either a neutron or an electron.

The correct option is this: IT IS EITHER A PROTON OR A NEUTRON.

Each atom of an element is made up of three sub particles, these are: electrons, protons and neutrons. The protons and the neutrons are located inside the nucleus of the atom while the electrons are located outside the nucleus, where they orbit round the nucleus. Since the sub particle X given in the question is located in the nucleus of the atom, then it is either a proton or a neutron.

c- cold periods in earth's history during which glaciers covered much of the surface.

explanation:

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.