Two different liquids are mixed together. which observation indicates that an exothermic chemical reaction has taken place?
a. an increase in volume
b. a decrease in volume
c. a rise in temperature
d. a drop in temperature

The  observation  which indicate  that an exothermic reaction  has taken place when two different  liquid are mixed  together is  a rise  in temperature  (answer C)

Explanation

 Exothermic reaction  is a   chemical reaction which releases  energy  in form of heat  or light.

  Examples  of   exothermic reaction is  a combustion reaction,  for instance combustion of methane which occurs as below.

CH4 +O2→  CO2 + 2H2O + heat

other  examples  of exothermic reaction is   neutralization reaction,  rusting of iron  and reaction between water and calcium  chloride.

a boiling water reactor does not boil the water. a pressurized water reactor boils the water faster. a pressurized water reactor is heated directly by the core. a pressurized water reactor does not use fission.

they it depends on if one believes about radioactivity, they make a geiger counter beep but maybe it was going to beep anyway electronics do wierd things all the time or it was programmed to beep near certain metals.