Of the following reactions, which is a fusion reaction?
a.
uranium-235 absorbing a neutron and splitting into xenon-140, strontium-94, and two neutrons
b.
hydrochloric acid combining with sodium hydroxide to form a salt and water
c.
carbon-14 decaying into nitrogen-14 and a beta particle
d.
curium-246 combining with carbon-12 to form nobelium-254 and four neutrons