A business letter typically includes both the date and address (heading) and the message with a signature, so both A & B are required.

A complete business letter typically includes both the date and address and the message and signature, so 'Both A & B' is correct.

The Partition of Bengal occurred in 1905 under British colonial administration.

The 1919 Government of India Act is known as the Montagu–Chelmsford Reforms, which introduced provincial dyarchy and expanded Indian participation in administration.

The Government of India Act transferred control of the East India Company's affairs to the British Crown, placing Indian administration under direct royal authority.

The Government of India Act (1858) transferred control of the East India Company’s administration to the British Crown after the 1857 uprising.

Kharaj was the land tax historically levied on non-Muslim cultivators and landlords in early Islamic administration.

Reliability and validity are the cornerstones of any standardized test. Reliability ensures that the test produces consistent results across different administrations and groups. Validity ensures that the test actually measures the specific construct or learning outcome it claims to measure. Without these two properties, a test cannot be considered a valid or useful tool for making educational decisions or comparisons.

The Battle of Khaybar occurred in 628 AD (7 AH). It was a significant military engagement between the Muslims of Madina and the Jewish tribes residing in the oasis of Khaybar. The victory at Khaybar was a strategic success for the early Islamic state, securing the northern borders and neutralizing a major source of opposition. This event is well-documented in Islamic historical records as a pivotal moment in the consolidation of power in the Arabian Peninsula.

The reign of Caliph Walid bin Abdul-Malik (705–715 CE) is considered the golden age of Umayyad expansion. Under his leadership, the Islamic empire reached its greatest territorial extent. Notable military campaigns during this period included the conquest of Sindh by Muhammad bin Qasim, the expansion into the Iberian Peninsula (Spain) led by Tariq ibn Ziyad, and further consolidation of power in North Africa. His administration oversaw a period of immense military success and cultural growth.