Option 1 states that both statement A and statement R are true, and that statement R is the correct explanation of statement A.

Statement A states that the major hot deserts of the world are located on the western margins of the continents. This is generally true. Hot deserts are often found in regions that are located in the interior of a continent, far away from the moderating influence of oceans. In these interior regions, the climate tends to be dry, with high temperatures and little rainfall. However, there are also some deserts that are located on the eastern margins of continents, such as the Arabian Desert in Asia and the Kalahari Desert in Africa. So, while statement A is generally true, it is not completely accurate.

Statement R states that the subtropical high pressure belt is well developed at the eastern margins of the oceans. This statement is not true. The subtropical high pressure belt is actually more well developed at the western margins of the oceans. This high-pressure belt is formed by descending air and is associated with the formation of deserts. The descending air creates a stable atmosphere that inhibits the formation of clouds and precipitation. Therefore, statement R is false and it does not provide a correct explanation of statement A.

In conclusion, option 1 is