From the given sentence, extract the phrase (often noun or verb) that carries the given relationship. The generated phrase should be present in the sentence.

Q: Given Relationship: 'be key to', Sentence: 'As present processes are thought to explain all past events , the Uniformitarianism slogan is " the present is the key to the past . "'

A: key
****
Q: Given Relationship: 'be town in', Sentence: 'The bridge would connect the Alaska town of Ketchikan to Gravina Island .'

A: town
****
Q: Given Relationship: 'be city of', Sentence: 'Houston is the biggest city in Texas with a population over 2 million .'

A:
city
****