The correct option is
C Both a and b
Coastal plain is a strip of land along ocean.
India with coastline of 75ookm has coastal plain stretching from Gujrat in West to West Bengal in East. According to their location they are classified as
Wetern coastal plain
Eastern coastal plain
WESTERN COASTAL PLAIN
Lying between Arabian Sea and western Ghats it stretches from south of river Tapi in North to Kanyakumari in South. Because of Esturine topography the coast is important for deep water ports(Mangalore, Mumbai) and electricity generation. Its subsections are
Gujrat coastal plain — Rann of kuthch plain
Konkan coastal plain — Mumbai-Goa
Kanara coastal plain — Karnataka
Malbar coastal plain — Kerala — famous for Coconut cultivation
EASTERN COASTAL PLAIN
Lying between Bay of Bengal and Estern ghats it stretches from mouth of Subernnarekha river in north to Kanyakumari in south. Many important rivers of country Ganga, Godavari, Krishna, Kaveri form Deltas in the region. Because of this reason the plain is important for agriculture particularly Rice (West Bengal Ganga, Tamil Nadu — kaveri). The sedimentary deposits harbours mineral resources like Coal, Petroleum as seen in Krishna-Godavari basin.
Its subsections are
Bengal costal plains — West Bengal
Utkal coastal plain — Odisha
Andra coastal plain — Andra Pradesh
Coramandel coastal plain — Tamil Nadu.