One of the four underlined parts marked A, B, C, D in each sentence is not correct in standard English. Define them.
31. would occur (A) => occured
32. (B) that must => that can
33. solving (C) => solved
34. others (C) => other
35. (A) so good => so well
36. that were (C) => which were
37. (C) considered a => considered a
38. (B) the people local => the local people
39. inhabit by plants (C) => inhabited by plants
40. after shortly (A) => shortly after