55. columnar joints in a basaltic lava flow are produced by which process? a. compaction of the flow during burial b. compression-related warming and expansion of the flow c. contraction and tension during cooling of the flow d. none of the above

C. Tension due to cooling of flow,

Explanation:

The correct option is: c. contraction and tension during cooling of the flow                              

Explanation:

Columnar jointing is a geological structure that is formed in igneous rocks by the cooling and contraction of the rocks and can also be formed in the cooling lava flows. In this process, the columns or the polygonal prisms are formed by the intersecting, closely-spaced fractures called joints.  

The columns formed can be straight or curved and 3 - 30 meters tall.

the answer is:

c. islam and christianity

explanation:

islam and christianity are widely practiced in africa. islam is practiced due to its spread from the middle east into africa, and christianity is practiced due to the colonization of africa by the british empire.