Explanation:

Let’s break down the rivers and the states:

- Option 1: Bihar

Ganga does flow through Bihar, but not for the majority of its length. Bihar gets a significant stretch, but not the biggest.

- Option 2: West Bengal

Ganga ends in West Bengal and forms the delta, but the river only travels a shorter segment here.

- Option 3: Uttarakhand and UP

This option nails it. The Ganga originates in Uttarakhand, but most of its journey is right across Uttar Pradesh. Combined, they cover by far the longest stretch of the river in India.

- Option 4: Punjab

Ganga never enters Punjab. This one’s just out.

So, what this really means is:

Option 3—Uttarakhand and UP—is the correct answer.