Uranium is the element used in nuclear power plants. It naturally emits particles from its nucleus. This releases energy that heats water to produce steam. The steam turns a turbine that produces electricity. The table below shows uranium-238 and thorium-234, the isotope that forms when the nucleus of uranium-238 emits a particle.

Isotope Uranium-238 Thorium-234
Protons 92
Neutrons 144
Electrons 92

How many protons and neutrons are emitted by Uranium-238 when it changes into Thorium-234?
A. 1 proton and 1 neutron
B. 2 protons and 0 neutrons
C. 2 protons and 2 neutrons
D. 2 protons and 4 neutrons