The father as well as his three children ____ skating on the frozen river every Sunday afternoon in winter.

______visited the Shanghai World Expo is sure to tell you the place is worth visiting twice.

 — Each of the students, working hard at their lessons, ______the book.  — So have I.

 One-third of the area ________ covered with trees. About seventy percent of the trees _______ been planted recently.

  the pencils ? They’re in the pencil box.