$28.$ $D$

- Câu đầu tiên của bài: "I began my teaching career nearly ten years ago".

$29.$ $D$

- Câu thứ $3$ của bài: "Sometimes I was very disappointed because of bad living conditions and low pay."

$30.$ $D$

- Câu thứ $5$ của bài: "However, at that time with my youth enthusiasm, I tried my best to devote myself to the noblest career that was "teaching".

$31.$ $B$

- Câu thứ $7$ của bài: " ... but I could not leave them alone to suffer from lack of schooling" (... nhưng tôi không thể để chúng một mình chịu cảnh thiếu ăn học).

$→$ Người giáo viên muốn những học sinh có được những kiến thức tốt.

$\text{1.}$D

→ Dẫn chứng : I began my teaching career nearly ten years ago.

$\text{2.}$D

→ Dẫn chứng : Sometimes I was very disappointed because of bad living conditions and low pay.

$\text{3.}$D

→ Dẫn chứng : However, at that time with my youth enthusiasm, I tried my best to devote myself to the noblest career that was "teaching".

$\text{4.}$B

→ Dẫn chứng : They were living in poverty, but I could not leave them alone to suffer from lack of schooling.