21 had( left ở quá khứ)
22 will take(nghĩa)
23 have been having(For the past six weeks)
24 will be travelling(câu bị động)
25 spends(HTĐ)
26 had been digging
27 burning
28 may have missed/might have missed(hasn’t come)
29 to know
30 could own/owned(wish+ V_ed)