In a polymerase chain reaction, temperature required for the steps (i) Denaturation, (ii) Annealing, and (iii) Extension are respectively.
A (i) 94°C (ii) 40°C (i) 72°C
B (i) 40°C (ii) 72°C (iii) 94°C
C (i) 94°C (ii) 72°C (ii) 40°C
D (i) 72°C (ii) 94°C (iii) 40°C

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Hint: Polymerase chain reaction is a technique broadly used to quickly make millions to billions of duplicates of a particular DNA test, permitting researchers to take a little example of DNA and intensify it to an enormous enough add up to investigation in detail.

Complete answer:
It is important to note that another technique that revolutionized the field of biotechnology called PCR. PCR stands for Polymerase Chain reaction. Arguably, the PCR machine has recently become indispensable to biological research as the light microscope was some 100 years ago. The idea of PCR was born only in the early 1970's but it took more than a decade before American biochemist Kary Mullis turned the idea into reality. PCR enables the production, or amplification of billions of copies of an original piece of DNA in a tube within minutes or hours not days.
Polymerase chain response (PCR) is a typical lab procedure used to make numerous duplicates (millions or billions!) of a specific locale of DNA. This DNA district can be anything the experimenter is keen on. For instance, it may be a quality whose work an analyst needs to comprehend, or a hereditary marker utilized by criminological researchers to coordinate wrongdoing scene DNA with suspects.

Polymerase chain reaction or PCR process includes three following steps:
1.Denaturation- This is the first step where DNA is heated at high temperature at 92℃ where two strands are separated from each other.
2.Annealing- This is the second step where to remove internal stresses and toughen, two oligonucleotide primers heated and then cooled down into the third end of single stranded template DNA. It requires temperature of 40°C
3.Extension- This is the third step where DNA polymerase extends the primers by the addition of nucleotides to form complete strands of DNA. It requires temperature of 72°

Hence, the correct answer is option (A)

Note: PCR was invented by American biochemist Kary Mullis in 1984 at the first biotechnology company at
California called Cetus Corporation. Ordinarily, the objective of PCR is to make enough of the objective DNA area that it very well may be broken down or utilized in some other manner. For example, DNA intensified by PCR might be sent for sequencing, envisioned by gel electrophoresis, or cloned into a plasmid for additional tests.

PCR is utilized in numerous zones of science and medication, including atomic science research, clinical diagnostics, and even a few parts of biology.