Why was lapis lazuli used only in the most
important artwork?

c

Explanation:

because it can enchant any tools you have  

Explanation:

but for real

Ground lapis lazuli was increasingly used by painters during the 13th and 14th centuries to make ultramarine and Cennino Cennini gives instructions on how to prepare this pigment in his “Book of Arts.” But it was not until the second half of the 16th century that large objects carved from lapis began to appear in Italy.

A. the Soviet Union was threatening to expand its influence.

Explanation:

Under the Truman Doctrine the help and assistance was insured to be provided to the countries facing the ills from the United States and the Soviet Union. The doctrine was entitled to provide economic and military assistance to Greece and Turkey. U.S. president Harry S. Truman took the step of helping these nations so as to counter the totalitarian forces against their aggressive nature. Such steps were taken in order to preserve the international peace and security.