is后面加什么時(shí)態(tài)

　　例句：

　　The clear inference is that the universe is expanding.

　　顯然結(jié)論是宇宙在擴(kuò)大。

　　It is essential that your diet is varied and balanced.

　　重要的是你的飲食應(yīng)當(dāng)是多樣而平衡的。

　　Today is Tuesday, so tomorrow is Wednesday.

　　今天是星期二，那么明天就是星期三。

　　It is a mild morning and the sun is shining.

　　這是一個(gè)和煦的早晨，太陽(yáng)在照耀著。