Final answer:
The verb or verb phrase that completes the sentence in the correct tense is 'will be quaking'.
Step-by-step explanation:
The verb or verb phrase in the correct tense to complete the sentence is will be quaking.
In this sentence, the action of being afraid and trembling is happening in the future, so the future progressive tense, using 'will be' + the present participle form of the verb, is appropriate. 'Quaking' is the present participle form of 'quake,' so 'will be quaking' correctly conveys the future tense and ongoing action described in the sentence.
For example: Tomorrow night when we take the ghost tour of the city, I will be quaking in my boots, hoping we don't actually see anything too spooky!
Learn more about English verb tenses