A.

26.. Lisa didn't go to school last week because she had a headache.

→→ because ++ mệnh đề nguyên nhân

→→ last week →→ thì  QKĐ: 

(+)(+) S + Ved/V2

(−)(-) S + didn't  + V-bare

27.. I feel pleased with my exam results.

→→ feel ++ adj: cảm thấy như thế nào

28.28. Although she studied hard, she failed the exam.

→→ Although ++ clause, clause: mặc dù...nhưng

B.

29.. Anna's mother is from China; however, she can't speak Chinese.

→→ clause ++ ; ++ however ++ , ++ clause: tuy nhiên...

30.Students must hand in their assignments on time.

→→ must ++ V-bare: phải làm gì