Sure! Here are the answers to the sentences provided:

31. Is living in the city **A. more convenient** than living in the country?
32. Mongolian children start to learn **A. horse riding** before they can walk.
33. On the side of the road, a herd boy was herding **C. cattle**.
34. He runs **C. faster** than his brother.
35. The Kinh have **A. large** number of people, accounting for about 86% of the population.
36. He couldn't buy any special food **D. because** he was very poor.
37. **B. Which** ethnic group has a larger population, the Tay or the Ede?
38. My father sometimes goes **B. hunting** in the forests. He'd like to find some more food for our family.

Let me know if you need anything else!