Which word group from the sentence is an infinitive phrase?

Read the sentences. the lowest point in antarctica appears to be the bentley subglacial trench, which is 8,200 feet below sea level. lower points may exist. which choice correctly uses the subordinating conjunction “although” to combine the sentences? the lowest point in antarctica appears to be the bentley subglacial trench, which is 8,200 feet below sea level, although lower points may exist. the lowest point in antarctica appears to be the bentley subglacial trench, which is 8,200 feet below sea level. although lower points may exist. the lowest point in antarctica appears to be the bentley subglacial trench, which is 8,200 feet below sea level although, lower points may exist. the lowest point in antarctica appears to be the bentley subglacial trench, which is 8,200 feet below sea level; although lower points may exist.