The tense of a sentence denotes a time, whether it is the time now (present), time then (past) or the time to come (future). The verb of a sentence has most to do with the tense. In the given sentence, we need to fill in a word that determines the correct tense. The action took place in the past "yesterday", hence a verb in the past tense is required. 'Stopped' is in the simple past tense, referring to an action that was completed in the past "yesterday", hence option D is correct. 'Was stop' is grammatically incorrect, 'was' is in the past continuous tense 'was stopping' whereas 'stop' is in the present tense, 'I often stop her from taking hasty decisions as she's impulsive' hence option A is incorrect. 'Stopping' is in the present continuous tense, whereas the action took place in the past, yesterday, hence option B is incorrect. 'Stops' is in the present tense, used in the third person point of view, 'she always stops me from taking the wrong decision', whereas the sentence is in the past tense, hence option C is incorrect.