Answer : The correct option is, (C) 45 degrees Celsius.
Explanation :
Endothermic reaction : It is defined as the chemical reaction in which the energy is absorbed from the surrounding.
In the endothermic reaction, the energy of reactant are less than the energy of product. During endothermic reaction, initially the temperature of the reaction is high because initially amount of heat is given to the system and after the reaction, the temperature of the reaction is low.
Exothermic reaction : It is defined as the chemical reaction in which the energy is released into the surrounding.
In the exothermic reaction, the energy of reactant are more than the energy of product. During exothermic reaction, initially the temperature of the reaction is low because initially there is no heat is given to the system and after the reaction, the temperature of the reaction is high because after ther reaction, more amount of energy is released.
As per question, a student performs an exothermic reaction in a beaker and measures the temperature. Initially, the thermometer reads 35 degrees Celsius. After the reaction, the thermometer temperature will be more that initial temperature that is, 45 degrees Celsius.
Hence, correct option is, (C) 45 degrees Celsius.