fill in the blanks with the correct tense of the verb in the bracket. mother was---to worry as my brother hadn't returned home.(begin).
Principal parts are
begin
began
begun
beginning
Which fits the sentence?
To fill in the blank with the correct tense of the verb, we should use the past continuous tense.
The past continuous tense is formed by using the past tense of the auxiliary verb "be" (was/were) and the present participle form of the main verb (verb + -ing).
In this case, the verb in the bracket is "begin."
The past continuous form of "begin" is "was beginning."
So, the correct sentence is:
Mother was beginning to worry as my brother hadn't returned home.