The only Sūrah in the Glorious Qur'an which must be recited in every obligatory prayer is

A.

al-Baqārah

B.

al-Alaq

C.

al-Fātīhah

D.

al-Ikhlās

Correct answer is C

Al-Fātiḥah (Arabic: الْفَاتِحَة‎, "The Opening" or "The Opener") is the first chapter (sūrah) of the Quran. Its seven verses (āyāt) are a prayer for the guidance, lordship, and mercy of God.
This chapter has an essential role in Islamic prayer (salāt). The primary literal meaning of the expression "al-Fātiḥah" is "The Opener," which could refer to this Surah being "the opener of the Book" (Fātiḥat al-kitāb), to its being the first Surah recited in full in every prayer cycle (rakʿah), or to the manner in which it serves as an opening for many functions in everyday Islamic life.