Concept:
India's onshore petroleum production is concentrated mainly in a handful of sedimentary basins, and the Cambay basin in Gujarat is one of the oldest producing regions in the country.
Explanation:
Ankleshwar, discovered in 1960 by ONGC, and Navagam (Nawagam), located near Cambay, are both well known onshore oil fields situated in Gujarat. Along with fields like Kalol, Nawagam and Cambay itself, they form part of the Gujarat oil belt that has been producing crude oil and natural gas since the early 1960s. Bihar has no major oil fields of this kind, West Bengal's hydrocarbon activity is largely limited to coal and some recent gas exploration, and Assam's famous oil fields are Digboi, Naharkatiya and Moran, not Ankaleshwar or Navagaon.
Final Answer:
Ankaleshwar and Navagaon are oil fields located in Gujarat, option A.