Answer:
Which verb indicates an inappropriate shift in tense?
b. will travel
Which tense should this verb be?
b. present
Step-by-step explanation:
The fact that comets travel around the sun must be referred to in the Present Simple tense, because it is something that is always true and happens regularly. Therefore, it cannot be indicated in the past tense or in the Present Perfect tense. Finally, the revised version of the first sentence is:
Comets are balls of ice and debris that travel around the Sun.