My mother ________ in the office since she __________(leave)the college

My mother ________ in the office since she __________(leave)the college

has been, left

My mother (has been) in the office since she (left) the college

My mother have worked in the office since she left the college.

My mother has been in the office since she left the college

My mother has been in the office since she left the college.

has worked left