The correct descending order of countries in terms of per capita availability of arable land is option 4: Brazil, India, China.

Arable land refers to land that is suitable for farming and cultivation. Per capita availability of arable land means the amount of arable land available for each person in a country.

In this case, Brazil has the highest per capita availability of arable land. This means that there is a relatively large amount of arable land available for each person in Brazil. India has a lower per capita availability of arable land than Brazil, indicating that there is less land available for farming per person. China has the lowest per capita availability of arable land among the three countries, meaning that there is the least amount of arable land available for each person in China.

So, the correct descending order of countries in terms of per capita availability of arable land is Brazil, India, China.

Alert - correct answer should be option 3: Brazil, China, India. The correct descending order of countries in terms of per capita availability of arable land is Brazil, China, India.