then and now对比表达 — 英语选择题

选出能表达“过去房间里没有电脑，现在有一台”的句子。A. There was a computer in the room then, and there is one now. B. There wasn't a computer in the room then, but there is one now. C. There is a computer in the room then, but there wasn't one now. D. There weren't a computer in the room then, but there is one now.