The trade across the Sahara Desert between the Arab merchants and West African Kingdoms was primarily based on an exchange of—

Salt and Gold

Explanation:

This was often referred to as the GOLD-SALT trade. The West African kingdoms have an abundance of golds.

This is evident in Ghana till the present moment and Mali during the time of Mansa Musa in the 14th century.

On the other hand, the Arab merchants have abundant salt for trading due to their nearness to the sea.

Hence, the right answer, in this case, is the trade was primarily based on SALT and GOLD.

hello there!

the graphics that you have attached within the question, indicates that few people in bolivia work in industry according to its labor force.

however, the graphic that is on the right side of the picture shows the gdp sector in bolivia. this gross domestic product is a macroeconomic magnitude   that shows the monetary value of all finished goods and services within a country's borders in a specific time period. in this case, the graphic is showing the monetary value in each sector -agriculture, industry and services- of bolivia in 2012.

so, although the first graphic located at the left side indicates that not so many people work in industry, this is the second most important sector according to the gdp metrics because of the monetary value that impacts on its country. it does not need to be the most valuable one. if it makes an impact on the country's economy, it will be definitely crucial to it.

he was able to speed up production of the processing of seeds