She said that the car 40 m.p.h. when it skid. (travel, begin) 17. fast today? you usually slowly. (you walk, walk) 18. this very strange noise. is all right ? (make, you think) 19. it for three days now. the roads will be blocked if it soon. (snow, not stop)
17. (ARE YOU WALKING, WALK)
18. (IS MAKING, DO YOU THINK)
19. (HAS BEEN SNOWING, DOES NOT STOP)