Choose the sentence that best expresses the following: 'I couldn't go to the party because I was ill.'
A) If I hadn't been ill, I could have gone to the party.
B) If I wasn't ill, I could go to the party.
C) If I weren't ill, I could have gone to the party.
D) If I am not ill, I can go to the party.
E) If I hadn't been ill, I can go to the party.
