Arrange the following in chronological order

A. Sri Lanka became an independent country
B. Formation of SAARC
C. Nepal adopted a new constitution
D. SAFTA came into effect

Choose the correct answer from the options given below:

A, B, D, C

The correct answer is option (4) - A, B, D, C

A. Sri Lanka became an independent country - 1948.
B. Formation of SAARC - 1985. 
D. SAFTA came into effect - 1st January 2006.
C. Nepal adopted a new constitution - 2015.