Answer : Photosynthesis is an example of a chemical reaction.
Explanation :
Photosynthesis : It is a type of chemical process which takes place in the plant cell. In photosynthesis process, the light energy converted into the chemical energy.
As plant needs carbon dioxide, water and light. During the photosynthesis, carbon dioxide, water and sunlight react to gives glucose, oxygen and water as a product.
The balanced reaction of photosynthesis will be,

Hence, photosynthesis is an example of a chemical reaction.
In step 2: Denaturation of the double-strand occurs.
In step 3: Annealing of the primer to the single strands.
In step 4: Extension or elongation takes place in this step.
Explanation:
In the PCR program an enzyme Taq Polymerase is used because it can withstand high temperature without altering its functions.
PCR is required for the amplification of DNA into multiple copies for experimental purpose. The artificial environment is created to form new DNA molecules from the sample in question.
The first step in replication is the opening of the double helix which is done by temperature treatment in PCR. The temperature would be 90 degrees for some 30 sec to two minutes.
The next step of primer annealing would be done at 52 degrees, this is the primer melting temperature.
The elongation of the DNA strand to be synthesized will take place at 72 degrees as Taq Polymerase can withstand that temperature.
Nearly one million copies of DNA will be made after 30 cycles of PCR.
PCR products can be stored at 4 degrees for some two months.
The correct answer for the given question above would be the second option. Based on the given scenario above about a fungal growth found on the nuts in a chocolate bar, the kind of a fungal infection could have infested the nuts would be <span>Aspergillus flavus. This is the kind of fungal infection that colonizes legumes and cereal grains. Hope this answer helps.</span>