In each of the following questions, sentences are given with blanks to be filled in with an appropriate word (s). Four alternatives are suggested for each question. Choose the correct alternative out of the four and indicate your choice for the correct answer.

Q:

But if a home-owner kills a burglar the ___________ is on him to prove that his use of force was reasonable.

• 1
  alacrity
• 2
  norm
• 3
  onus
• 4
  backdrop