The correct option is A Was coming
The past continuous tense, also known as the past progressive tense, refers to a continuing action or state that was happening at some point in the past.The past continuous tense is formed by combining the past tense of to be (i.e., was/were) with the verb's present participle (-ing word), that is, was coming. The action of coming was happening at some point in the past. Hence, Option A is correct. The rest of the options mention continuous actions in the present (options C and D) and in the future (option B). Hence they're incorrect.