The correct option is C Of / between
The first part of the given sentence talks about the link.
'In' and 'For' is not used to show 'about'. We can thus eliminate options A and B as incorrect options.
Of is used to indicate possession, relation, substance, cause or about.
Thus 'of' must fill the first blank of the given sentence.
Between is used into the space separating two different things. Here, a separation is indicated between emotions and backaches. Thus between must fill the second blank of the given sentence.
Thus option C is the correct answer.