No, 'explain' is present tense. The past tense is explained.
Explain is a verb.
The past tense of the verb 'am' is 'was' or 'were.' The verb 'am' is derived from the verb 'to be.'
The past tense verb for "do" is "did."
Yes, it is a form of the verb "to explain" (clarify, or justify). It is the past tense and past participle, and might be used as an adjective (explained mysteries).
By is not a verb and does not have a past tense. Buy is a verb, and the past tense is bought.
The verb is still "to be", regardless of the tense. It is an irregular verb, and the past tense forms are was for I and he/she/it, and were for we, you, and they.
The past tense of explain is explained.
"Shook" is the past tense of the verb, "to shake".
The past tense of the verb to promise is promised.
reside is the verb. Resided is the past tense.
The past tense of the verb take is took
The abbreviation for the past tense verb is "past."