2006 — Twitter was launched in 2006, so 2006 is the correct answer.

Hajj is the fifth pillar of Islam because it is the obligatory pilgrimage to Mecca that Muslims must perform once if they are physically and financially able.

Twitter was launched in 2006, which is the year the platform began operations.

Abu Sufyan — he led the Quraysh forces opposing the Muslims at the Battle of Uhud, so Abu Sufyan fits as the commander of the infidels in that battle.

Quaid-e-Azam resigned from the Indian National Congress in 1920, the year he formally left the party to pursue separate political work for Muslims.

Duplicate of Q35. Violence in Kolkata (Guha).

Direct Action Day sparked widespread violence in Kolkata (Calcutta), per historical accounts (e.g., Guha, “India After Gandhi”).

The Charter of Medina (Mithaq al-Madina), drafted in 622 CE, established civic rights, common defense, and judicial authority among Muslims and Jewish tribes in Madina.

The funeral prayer is a collective communal obligation (Fard al-Kifayah); if a group of Muslims performs it, the obligation is discharged for the entire community.

In 2006, Dick Cheney was the incumbent Vice President of the United States, serving under President George W. Bush [1, p13]. Cheney held the office from January 20, 2001, to January 20, 2009. The provided PDF's answer key incorrectly marks (d) and its explanation is not relevant to the 2006 timeframe [1, p13].