In the construction of arches, sand box method is used for A. Centring B. Actual laying of arch work C. Striking of centring D. None of the above

The correct answer is: A. Centring

Centring is the temporary support used to hold the weight of the arch until the mortar has set. The sand box method is a type of centring that uses sand to support the arch. The sand is placed in a box that is shaped like the

arch, and the arch is then built on top of the sand. The sand provides support for the arch and helps to keep it in place until the mortar has set.

The other options are incorrect because:

• Option B, actual laying of arch work, is not the purpose of the sand box method. The sand box method is used to support the arch, not to lay the arch.
• Option C, striking of centring, is the process of removing the centring after the arch has been built. The sand box method is not used for striking of centring.
• Option D, none of the above, is incorrect because the sand box method is used for centring.