Explanation:

4th statement is correct regarding red soil i.e. It is rich in iron compounds
Red soil is a type of soil that develops in a warm, temperate, moist climate under deciduous or mixed forests, having thin organic and organic-mineral layers overlying a yellowish-brown leached layer resting on an illuvial red layer.
They are usually poor growing soils, low in nutrients and humus and difficult to cultivate because of its low water holding capacity.