Choose the revised sentences that correct the pronoun reference problem in the sentence below. Select all that apply. "Although this is common writing advice, I find it difficult to implement."
a) Our professor explained that we should allow time for revision, and although this is common writing advice, I find it difficult to implement.
b) Although this is common writing advice, it can be difficult to implement.
c) Although this is common writing advice, I find this difficult to implement.
d) Although allowing time for revision is common writing advice, I find it difficult to implement.