Refer to figure.
Whilst there are some requirements for an obstacle accountability area in VFR operations, a lot of the obstacle clearance requirements are removed due to the fact that an engine is not assumed to fail in VMC conditions. It is usually assumed that an engine will fail at the cloud base, but the visual conditions negate that requirement, as if an engine did fail, it is assumed that the pilot would be able to complete a visual flight on one engine to return for a landing, or head to a nearby alternate, remaining clear of obstacles visually.

As the other options are quite confusing, it is useful to go though each of them individually.

• "is at least 60 m wide from the end of the TORA, gradually extending to a maximum 300 m width along the planned flight path."
  • The obstacle accountability area has a half-width of 60 m + 1/2 wingspan. This is not its full width, instead we measure everything from the middle to the edge, as that is the horizontal distance from the assumed aircraft location. Even if the examiner said 60 m half-width, then 300 m would still be incorrect, as part (C)(1) above mentions 600 m when a track change >15° has been made after departure.
• "is effectively substituted by ensuring the weather conditions during operation are sufficient to visually navigate and avoid obstacles."
  • Whilst this is a little bit of a leap, it is still the most correct answer present, as VMC conditions do allow for much reduced obstacle clearance criteria to be accounted for, in a couple of ways.
• "commences at the assumed engine failure height and will gradually widen as the distance along the flight path increases."
  • The obstacle accountability area commences at the end of the TODA, or the end of the TOD if there is a turn scheduled before the end of the TODA.
• "commences at the end of the TODA and consists of a 90 m wide corridor along the flight path until the aeroplane reaches 50 ft above any obstacle."
  • The obstacle accountability area is not 90 m wide (remember we work in half-widths) and increases in width gradually, and runs until the aircraft has reached 1500 ft.