The question asks for the correct order of the tributaries of river Ganga from east to west. Let`s analyze each option to determine which one is correct.

Option 1: 3-4-1-2

This option suggests that Ghaghara is the easternmost tributary, followed by Gomti, Gandak, and finally Kosi. However, this is not correct as Kosi is actually located further east than Ghaghara.

Option 2: 2-1-3-4

According to this option, the correct order is Kosi, Gandak, Ghaghara, and then Gomti. This option is correct, as Kosi is indeed the easternmost tributary of river Ganga, followed by Gandak, Ghaghara, and then Gomti.

Option 3: 2-3-1-4

This option suggests that Kosi is followed by Ghaghara, then Gandak, and finally Gomti. However, this is not the correct order as Gandak is located between Kosi and Ghaghara.

Option 4: 1-2-4-3

According to this option, the correct order is Gandak, Kosi, Gom