Answer: The inflection mof the verb "occured" is -ed, which indicates past tense.
Explanation: The -ed inflection is used to indicate past tense, that is to say to refer to an event or situation that took place before the present time. In contrast, the -s or -es inflection is used to indicate present tense. In that way, the ending "-ed" has been added to the base form "occur" to indicate past tense and; therefore, to indicate past time.
