Which of these fits gap 20?

Directions: Complete this passage by selecting the most suitable option for the corresponding gap.
The word ‘petroleum’ _____ (17) _____ from the two Latin words ‘petra’ and ‘oleum’ meaning rock and oil respectively.
Intense pressure and heat inside the earth converted the decomposed plants and animals _______ (18) ______ petroleum.
Scientists have ______ (19) ______ in synthesising petrol by some artificial techniques also, but petrol prepared in this way is costlier.
It is found in many countries but mainly in Gulf countries, USA and Russia. In India, it is _____ (20) ______ found in Assam and Bombay High.