A simple question, trying to say, let's have a lesson from 4 to 5 -- want to make sure that "to" is indeed 到.
到 is OK. You could also use 至. 到 is more colloquial. In many cases they are interchangeable, for example: 从古到今/从古至今（from ancient times to the present）, 直到此刻/直至此刻（up to now）. But you could only say 自始至终（from the beginning to the end），从这到那（from here to there） because 自始至终 and 从这到那 are kinda like set phrases.