They're. They are driving to Yellowstone National Park tomorrow. Theirs doesn't sound right in the sentence. Their means belonging to. So they're fits in the sentence the best.
The answer is true because if you have experience you can look back on the day it happened.
Verbal and nonverbal cues can give us as human beings many different subtle cues as to what's going on in social situations. For example, certain nonverbal cues such as yawning, stretching, dreary eyes, and a hunched over body position can cue a person in rather quickly that this person is probably overtired. Furrowed eyebrows or extended staring at a specific object, or situation can help us infer that someone is perplexed. A hurried gesture, with sweeping movements of the hand towards the body implies that they want you to come towards them quickly.
Verbal cues are more obvious as thy state points more clearly, but both are efctive tools in language that we often overlook.
