A．用方框中所给单词的适当形式填空，每词仅用一次（每空一词）

speech          smooth        our              until       divide

46．I didn't learn to paint 　　I was forty．

47．The students were 　　 into four groups before doing experiments．

48．James looked tired，for he listened to three 　　this morning．

49．I'll lead you to your room．　　 is the one next door．

50．There is no wind and the water is as 　　 as glass．