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:

The vehicles involved in the accident were _______________ the flow of traffic.

• 1
  delaying
• 2
  boosting
• 3
  interfering
• 4
  obstructing