Explanation:

• Teesta River originates from the Pahunri (or Teesta Kangse) glacier above 7,068 m, and flows southward through gorges and rapids in the Sikkim Himalaya.
• It flows through Sikkim and West Bengal to merge with the Brahmaputra in Assam 
• Teesta River is considered to be the lifeline of the Sikkim.
• The basin lies in the states of Sikkim (72.43%) and West Bengal (27.57%). 
• The main tributary of river Teesta is the Rangeet River.
• Teesta River makes a border between Sikkim and West Bengal before joining the Brahmaputra as a tributary in Bangladesh.

Hence only statements 1,2&4 are correct.