"The long word-for-word agreements between Matthew and Luke are easy to explain as sayings people memorized and passed on by word of mouth." Agree or disagree?

Disagree. Long stretches of word-for-word agreement are hard to explain by memory alone. Q is the idea of a lost source behind Matthew and Luke, and scholars who hold it say Q must have been a written document. Those who reject Q say Luke had Matthew's text in front of him.