Sun has burned half of hydrogen in:

The Sun is approximately 4.6 billion years old. It is currently in its main-sequence phase, where it fuses hydrogen into helium in its core. Scientists estimate that the Sun has already consumed about half of the hydrogen fuel in its core during this period. Therefore, the correct option is B: 4.6 billion years.

• Options A: 3 billion years, C: 5.5 billion years, and D: 6.1 billion years are incorrect as they do not accurately represent the current estimated age of the Sun and the amount of hydrogen it has consumed. The Sun is expected to continue burning hydrogen for another 5 billion years.