26. is$\to$be
27. in $\to$on
28.going to$\to$ is going to
29. has $\to$have
30.one - once
31.two times - twice
32.speak - speaking
33.do - does
34.to -$\varnothing$
35.lesson - lessons
36.does - did
37.do- did
38.go - went
39.don't - didn't
40.don't - doesn't
41.visits - visit
42.goes - go
43.on - in
44.you - your
45.nam birthday - nam'sbirthday
46.have - had
47.on - by
48.go- went (go ở câu trả lời)
49.are - were
50.on - in