Here option A controlled experiment is the correct answer
A Controlled experiment is the one with one dependent variable and one experimental variable. A controlled experiment is simply and experiment in which one variable is kept independent and all other factors are kept constant. The advantage of controlled experiment is that it makes easier to eliminate uncertainty about the significance of the result.
The correct answer is 10 billion years. The Sun is expected to undergo hydrogen fusion for a total of 10 billion years. The Sun generates its energy by nuclear fusion of hydrogen and produces helium nucleus. It fuses 620 million metric tons every second.
