For more information on the “Sijjin”, please see Chapter 83 – Surah Al Mutaffifin (The Defrauders), verses 7-9.
You may wish to read Surah Al Zalzala along with this surah.
You may wish to read Surah Al Kahf (The Cave) before reading this verse.
Thus the questions asked by the Meccans were answered by Prophet Muhammad (peace be upon him), as he was supposed to. In spite of this, the Meccans did not believe in his Prophethood, and as explained in verse 55 of Surah Kahf, were stubborn till the very end.
This concludes Surah Kahf. The first two questions asked by the Meccans were answered by verses from this Surah. The final question, regarding “Ruh”, was answered in Surah 17, verse 85.