Unrestricted submarine warfare
Answer:
One of The 5 Pillars of Islam
Explanation:
As described in the Quran, making the pilgrimage to Mecca is one of the five pillars of Islam instituted by Allah. In this sense, Hajj is carried out for the love of God and to be forgiven for all his past sins, In this sacred place that is the most important in the Muslim world. The pilgrimage is one of bases and principle of the Muslim religion.
I believe the answer would be C, burning fossil fuels. Oil and gas is made up of the remains of microscopic plankton. Over millions of years the remains become the carbon-rich coal, oil and gas we can use as fuel. When fossil fuels are burned they release carbon dioxide into the atmosphere, thus contributes to global warming.
Li Yuan who became emperor Gaozu <span />