In general, the most materially advanced and developed countries are focused on extensive development of the sector of their economy.

a. quaternary
b. secondary
c. tertiary
d. primary

Answer primary waves;

Answer islamic scholars made advancements in technology, literature, philosophy, mathematics, astronomy, and the arts during this time period;

Historians are researchers of the past or people who understand the history of people. with this field, they must possess qualities such as being unbiased, patient, efficient reader, has a knack for logic and critical thinking and reasoning, disciplined, open-minded, resourceful, with good analytical ability, good reasoning skills and problem solving!

The answer is d., a mountain.