Explanation:

- The bill is payable 100 days after sight, sight being on 4th May 2017.

- Counting starts from 5th May. Adding 100 days brings us to 13th August 2017.

- As per Negotiable Instruments Act, add 3 days of grace. 13th + 3 = 16th August 2017.

- 15th August is a public holiday (Independence Day in India), so maturity moves to next working day, if it falls on a holiday.

- However, 16th August 2017 is a working day.

Option 1: 13 August, 2017 (Only 100 days, no grace period)

Option 2: 14 August, 2017 (100 days + 1 grace day)

Option 3: 15 August, 2017 (100 days + 2 grace days and public holiday)

Option 4: 16 August, 2017 (100 days + 3 grace days, next working day after holiday)

Correct answer: Option 4 - 16 August, 2017