The correct chronological order of the invasion on ancient India is Greeks, Sakas, and then Kushans, which is reflected in option 1.

In the 4th century BC, Alexander the Great initiated the Greek invasions into India. After his death, his Indian conquests were taken over by the Seleucids and then by the Greeks of Bactria.

The Sakas, or Scythians, were a group of nomadic tribes from Central Asia who invaded north-western India in the 2nd century BC, following the path set by the Greeks.

The Kushans, originally from Central Asia (modern China), invaded India from the first to the third century AD. The most prominent ruler of the Kushans was Kanishka, known for his patronage of Buddhism.

Option 2, Option 3, and Option 4 are incorrect as they do not fulfill the chronological order of invasion. Therefore, the right answer is Option 1: Greeks-Sakas-Kushans.