In the following question, two statements and five connectors are given. Only one of the connectors from those given can be used to combine the given two statements into one sentence without changing the meaning. Choose that connector as your answer.
I. The pair met every day for a few weeks after their first encounter.
II. Clibbery helped Packwood care for her dying mother and she then looked after him after his kidney operation.

The given sentences are sequential in nature. Sentence I seeks to convey that the two people met on a regular basis after their first meeting. Sentence II tells us that following these regular meetings, Cliberry helped Packwood (one person helped the other) care for her dying mother, and later on, Packwood took care of Cliberry when he had a kidney operation. BEFORE is used to show that one action took place earlier than another one (here the starting of their friendship is the first action and the second event is described as the one in which both of them helped each other) and can be used to join the two sentences: "The pair met every day for a few weeks after their first encounter, before Clibbery helped Packwood to care for her dying mother and she then looked after him after his kidney operation." Thus, D is the right answer.