Answer:
a. It consists of a billion people making $2,000 to $20,000 a year.
Step-by-step explanation:
The global economy pyramid is divided into three levels, which are called three tiers.
Under tier 1 only people having income more than $20,000 are present, and generally they live in developed economies, like: Western Europe, Japan, etc:
Under tier 2 people having income more than $2,000 and less than $20,000 are found, these are around 1 billion in population.
Under tier 3 maximum population lives, which is approximately 4 billion people.
Therefore, the correct statement is :
a. It consists of a billion people making $2,000 to $20,000 a year.