虚拟假设的基本句型 — 英语选择题

Tom没有闹钟，所以昨天上班迟到了。下列哪一句正确表达了他的虚拟假设（与现在事实相反）？A. If Tom has an alarm clock, he wouldn't be late. B. If Tom were to have an alarm clock, he won't be late. C. If Tom had an alarm clock, he wouldn't be late for work. D. If Tom would have an alarm clock, he isn't late for work.