As a star forms at what point do nuclear reactions begin to occur

Shouldn't this be under physics ?

But the energy of the stars comes from nuclear fusion processes. For stars like the sun which have internal temperatures less than fifteen million Kelvin, the dominant fusion process is proton-proton fusion. For more massive stars which can achieve higher temperatures, the carbon cycle fusion becomes the dominant mechanism. For older stars which are collapsing at the center, the temperature can exceed one hundred million Kelvin and initiate the helium fusion process called the triple-alpha process.

So Stage 3, Hydrogen fuses to form helium and nuclear reactions begin to occur.

Taking a shower. why is cause as you shower the water is running more than taking a bath, washing a load of dishes or brushing your teeth. water is being used more by taking a shower and depending on how many people live in the household that take showers. some take a shower twice a day.