题目

 It took me about half ____  hour to walk to _____ cinema.   A. an; the     B. a; the    C. an; a   D. a; a 答案：A如图4，正方形ABCD中，E是AB上任一点，作EF⊥BD于F，则EF︰BE=（    ）A．B．C．D．