Option 1 -> Lumbinivana (Lumbini) is the birthplace of Gautama Buddha in present-day Nepal.
Option 2 -> Sarnath is where Buddha delivered his first sermon, known as Dhammacakkappavattana Sutta (Setting in Motion the Wheel of Dharma), to his five former companions.
Option 3 -> Bodh Gaya is where Buddha attained enlightenment under the Bodhi tree after years of meditation.
Option 4 -> Kushinagar is where Buddha attained Parinirvana (passed away) at the age of 80.
Hence, Option 2: Sarnath -> After attaining enlightenment at Bodh Gaya, Buddha traveled to Sarnath (near Varanasi) and delivered his first sermon at the Deer Park (Isipatana), where he explained the Four Noble Truths and the Eightfold Path to his five ascetic companions, marking the beginning of his teaching ministry -> correct