What is the difference between <i>did </i>and <i>would</i>?<br/><br/>Please take a look at the link below:<br/><br/><a href='http://books.google.com/books?id=A5VBQ3I21TIC&pg=PA101&dq=in+the+morning+the+man+and+woman+were+sitting&ei=xl-RSejsDo_GlQSIlbXTCg#PPA101,M1' target='_blank' rel='nofollow'>http://books.google.com/books?id=A5VBQ3I21TIC&pg=PA101&dq=in+the+morning+the+man+and+woman+were+sitting&ei=xl-RSejsDo_GlQSIlbXTCg#PPA101,M1</a> <a href="http://books.google.com/books?id=A5VBQ3I21TIC&pg=PA101&dq=in+the+morning+the+man+and+woman+were+sitting&ei=xl-RSejsDo_GlQSIlbXTCg#PPA101,M1"></a><br/><br/><br/>Page 101, line 2, there's a sentence that reads, "They would not move." Why does it have to be <i>would, </i>instead of <i>did</i>?