Explanation:

Bhasan Char, the site where Bangladesh has begun sending Rohingya refugees from the overcrowded camps at Cox’s Bazar, is an island formed by sedimentation (char is Bengali for sediment) close to the coast.

• It is estimated that more than 8 lakh Rohingya, who fled an army crackdown in Myanmar’s Rakhine Province in 2016 , live in the camps at Cox’s Bazar in unhygienic conditions.
• Bangladesh’s plan is to move some 1 lakh refugees to Bhasan Char, 39 km from Naokhali on the mainland.
• Prime Minister Sheikh Hasina said it would be a temporary measure. One of her ministers said those relocated to the island would not be allowed to leave from there unless they are going back to Myanmar. The decision has evoked international concern.
• Bhasan Char is less an island and more mud flat, and is vulnerable to going under water from tides and flooding. Much of it is submerged during the monsoon.
• Located near the mouth of the river Meghna where it flows into the Bay of Bengal, Bhasan Char surfaced only in 2006 from the sediment deposited by the river.
• Located close to the much larger Sandwip, Bhasan Char spans 40 sq km.

Hence option 1st is correct.