The correct option is D just
'Just' is used as an adverb which shows something has happened a short time ago. 'Just' is an adverb of degree which usually goes in the mid position before the verb. 'Yet' is an adverb of time which is used to show that something has not happened by a particular time. 'Since' is used to show something at some time after a particular point in the past. Thus, option C is the correct answer.