A PCR machine can raise temperature upto `100^@C` but after that it is not able to lower the temperature below `70^@C` automatically. Which step of PCR will be hampered first in this faulty machine explain why?

Most living orgnisms can not survive at temperature above 45^@C . How are some microbes able to live in habitals with temperature exceeding 100^@C ?

What happens after point D in temperature - time graph? Can steam be hotter than 100^@C ?

Three objects coloured black, gray and white can withstand hostile conditions upto 2800^(@)C . These objects are thrown into a furance where each of them attains a temperature of 2000^(@)C . Which object will glow brightest?