Percentage share of plains in the total land area can be calculated by dividing the area of plains by the total land area and then multiplying by 100.

To explain this answer, we will break it down into the following sections:

1. Calculation of the area of plains
2. Calculation of the total land area
3. Calculation of the percentage share of plains in the total land area

1. Calculation of the area of plains:
To determine the area of plains, we need to know the total area of plains and the total area of the region in consideration. Unfortunately, the question does not provide this information. Therefore, we need to assume or refer to a reliable source for the percentage share of plains in the region.

2. Calculation of the total land area:
Similarly, the question does not provide the total land area of the region. To solve this, we need to refer to a reliable source that provides the total land area data for the region in question.

3. Calculation of the percentage share of plains in the total land area:
Once we have the area of plains and the total land area, we can calculate the percentage share of plains by using the following formula:

Percentage Share of Plains = (Area of Plains / Total Land Area) * 100

Explanation of the Correct Answer:
The correct answer provided in the question is option 'A', which states that the percentage share of plains in the total land area is 43%. However, without the specific data regarding the area of plains and the total land area, we cannot verify the accuracy of this answer.

Therefore, it is important to note that the calculation of the percentage share of plains in the total land area requires specific data and cannot be accurately determined without this information.