1. Our cat understands everything-he's nearly human. This seems OK to me. I'd put a space on either side of the dash. Actually, I'd prefer to make it two sentences. But, it seems basically OK. It's OK to call your cat 'he', if it's not a 'she'.
2. All along the journey she kept complaining. Comma after journey
Now the questions are worked out. but i'd like to say that these are bad questions for an entrace exam designed for English majors who would like to apply for postgraduate programme in English literature.