Answer:
...if the route was too steep and dangerous
Explanation:
The above text in the sentence functions as an adverb clause. This is true because an adverb clause is known to be a group of words that actually performs the work of an adverb. But the group of words must contain a subject and a verb in order to be a true clause.
Adverb clauses actually add information which helps to describe verbs, adjectives and even adverbs. These clauses show the when, where, how, why, how much or the condition at which the action took place.
The above text actually gives more information about the 'route' and its condition that will make Tina make her decision. So, it is the correct text.
