Which best describes the term five pillars?
a. the successors to muhammad who spread his teachings
b. the columns that support the entrance to a mosque
c. the caves near mecca where muhammad had a vision
d. the special religious duties a muslim must observe
d?

One of the Five Pillars of Islam is the prayer - so it's an activity, not a place or an object or people. Because of this already we can reject the first three options: the first one describes a person, the second an object and the third a place.

The correct answer is d). It also inludes giving to charity and a pilgrimage to Mecca.

from the conditions of the working class in england by friedrich engels,the main idea is :

manchester's leaders hoped to oppress its working class to benefit factory owners.

South carolina was so angry about the election of lincoln that they seceded from the union on december 20, 1860. they attacked fort sumter later, on april 12, 1861.