The correct answer is b) Monazite.
Monazite is a rare earth phosphate mineral with the chemical formula (Ce,La,Nd,Th)(PO4) and is the most important source of the rare earth elements. It is a heavy, black mineral that is often found in beach sands. Monazite is also found in some igneous and metamorphic rocks.
Ilmenite is an iron titanium oxide mineral with the chemical formula FeTiO3. It is a common accessory mineral in mafic and ultramafic igneous rocks, and it is also found in some sedimentary rocks. Ilmenite is an important source of titanium.
Rutile is a titanium dioxide mineral with the chemical formula TiO2. It is a common accessory mineral in igneous rocks, and it is also found in some metamorphic rocks. Rutile is an important source of titanium.
Zircon is a zirconium silicate mineral with the chemical formula ZrSiO4. It is a common accessory mineral in igneous rocks, and it is also found in some metamorphic rocks. Zircon is an important gemstone and it is also used as an abrasive.
In the coastal sandy soils of Kerala, monazite is the most abundant mineral. It is a heavy, black mineral that is often found in beach sands. Monazite is also found in some igneous and metamorphic rocks. Monazite is an important source of the rare earth elements.