Explanation:

- Section 101 of the Indian Evidence Act defines who has the responsibility to prove a fact in court, known as the "burden of proof."

- Option 1: never shifts – This means the burden of proof stays with the same party throughout. ? This is not accurate because the burden can move depending on how evidence unfolds.

- Option 2: goes on shifting as the trial proceeds – Sometimes the burden of proof moves between parties as new evidence is introduced.

- Option 3: may shift – The burden doesn't always shift, but it can in certain circumstances.

- Option 4: both b and c are correct – Both these options highlight that the burden may or does shift during trial.

Correct answer: Option 4: both b and c are correct