deleting rows that have dublicate data in certain collumn

would samone help me about this situation


Collumn A Collumn B
200------------------sa
200------------------bg
300------------------zo
200-------------------ch
200--------------------fr
300--------------------dr
100--------------------ei
400--------------------lm

Must be look like that

100----------------- ei
400----------------- lm

Are there chances of having 3 occurrences of 200? If so, should 2 be deleted and 1 retained?