The Fault in Our Stars: Why do Augustus and Hazel sign off their phone conversation with “okay”? What is the meaning of the “third space” visited on the phone?

Excerpt from the trip of a lifetime elizabeth mohn 3 a little more than a week ago, my mother and father started packing our suitcases to prepare for our trip. my entire family woke up early sunday morning, packed the car, and began our expedition to niagara falls. when we reached the american-canadian border, i was excited to enter a foreign country for the first time. the third paragraph is mainly about a) traveling to niagara falls b) leaving the hotel. c) seeing the falls. d) returning home.