-I'm sorry I wasn't able to come early. Why couldn't you? -By the time I got to the station the school bus had left.Then I had to wait another twenty minutes before I managed to get on a public bus. 4.Substitute: 1)-I'm sorry I wasn't able to get the film magazine for you. -Why couldn't you? By the time I got to town the bookstore had all closed.—I’m sorry I wasn’t able to come early. — Why couldn’t you? — By the time I got to the station the school bus had left. Then I had to wait another twenty minutes before I managed to get on a public bus. 4. Substitute: 1) — I’m sorry I wasn’t able to get the film magazine for you. — Why couldn’t you? — By the time I got to town the bookstore had all closed