could anyone help me to look for the errors of these sentences and give the reasons why ? and make sure your answer, please don't just take the points!

29. C
use gerund after preposition, not infinitive
31. A
we need a noun here, not an adjective
32. B
we need a adverb here to modify the adjective, not another adjective
33. B
problem should be in plural form.
34. D
it should be in past participle like the word diluted
35. B
the subject is plural so the verb should not be in the singular form
36. B
grassy plants, not plant grassy
37. D
it should be in the past participle because of the passive meaning
38. C
balance is a verb, it should be preceeded by to, not for
39. D
there shouldn't be a the there
40. D
after subject (they) use a verb, not a noun, as predicate.