During a certain six-year period, the consumer price index (CPI) increased by 50%, but during the next sis-year period, it increased by only 30%. Which of these conditions must have existed during the second six-year period?
A. Inflation
B. Stagnation
C. Conflation
D. Deflation

D. Deflation

Explanation:

"Consumer Price Index" (CPI) measures the changes in the weighted average of prices of a market basket (consisting of consumer goods and services). It tells the cost of living for every consumer.

"Inflation" refers to the sustained increase of prices of goods and services while "deflation" refers to the sustained decrease of prices of goods and services.

In the situation above, the CPI is considered lower than before, thus deflation must have occurred during the second six-year period. It shows a negative inflation rate.

So, this explains the answer.