The correct answer is by adding “studying for” to the beginning.
A parallel construction means that the same form of a word is used throughout a particular sentence. Since we can see that the latter part is 'completing my homework,' it would be good to add a verb to the first part as well, in order to make the sentence parallel. By adding 'studying for,' we've added the same form of a verb (ending in -ing).
<span>The Religious shift that took place when Oedipus was king was a gradual one. It started with the poor people them move up to the rich. The king himself was the last one to give up his god.</span>
