Petroleum. For details about the chemistry you might wish to consult the benzene page on wikipedia.
Comets have two main sources, the Oort Cloud or the Kuiper Belt
The two main sources of genetic information are DNA and RNA. DNA carries the genetic instructions for all living organisms, and RNA helps in the process of translating these instructions into proteins.
The two main sources of blood stem cells are bone marrow and peripheral blood. Bone marrow is the primary site for hematopoiesis (the formation of blood cells), while peripheral blood can be mobilized to contain stem cells, often collected during apheresis procedures. Additionally, umbilical cord blood is also a source, but the primary sources remain bone marrow and peripheral blood.
A major source of conflict in the Muslim Middle East is the divisive nature between the two main sects of Islam: Sunni and Shi'a. Although these two sects agree on the fundamentals of Islam and the teachings of the Quran, they are in conflict about who would lead the Muslim community after Muhammad's death.
I'd have to say Christianity for certain and with the rise of Islam, then Islam is number two.
Islam or Christianty
The two main groups of Islam are the Shia and Sunni. They divided into these groups after Mohamed died and they could not decide on just one successor.
The two main branches of Islam in Iraq are Sunnis and Shiites. However, both branches share many common Islam principles and rules. Refer to related question below.
The holy Quran & the Hadith are the first main sources of legislations in Islam,respectively.
islam
Christianity and Islam
The two main sources in water vapor are farming and manufacturing
It is Islam religion. Muslims are belonging to the main two different schools: Shiites and Sunnis.
it is more accurate in religious sciences if we apply sect instead of branches.therefore we have to say in Islam religion we have two sects,shiite as minority and Sunni as majority.Sunni and shiism are two main sects of islam religion.
they are two sect or fraction of Islam religion. Sunnism as Majority and Shiite as minority are two main sects in Islam religion.
The main two branches of Islam are Sunnis and Shiites. Refer to related question below for the difference between the two.