is a conventional sign of

ANS:D - idgah.

The answer should be mosque because the mosque has a curved shape in the middle with pillar structure around and Idgah has a flat roof surrounded by two Pilar. Eidgah or Idgah is a term used in South Asian Islamic culture for the open-air enclosure usually outside the city (or at the outskirts) reserved for Eid prayers offered in the morning of Eid al-Fitr. Both are similar to appearance but musjid only have three pillar structure and idgah have two pillar structure. Eidgah or Idgah is the term used in south Asian Islamic culture for the open-air gathering place usually outside the city (or at the outskirts) to perform the Salat al Eid (Eid prayers) for Eid ul-Fitr and Eid al-Adha. It is usually a public place that isn't used as a mosque at other times of the year.