unit 10 Frightening nature
(2) help 當“幫助”講時，后面的賓語或賓補的不定式符號to可帶可不帶.
i will help (to) do it for you.
i will help you (to) do it.
（3）介詞but前若有動詞do,后面的不定式不帶 to.
the boy did nothing but play.
(4) 某些使役動詞（let, make, have）及感官動詞（see, watch, hear, notice, observe, feel, look at, listen to等）后面作賓語補足語的不定式一定要省去 to, 但在被動語態中須將to 復原。
i saw the boy fall from the tree.
the boy was seen to fall from the tree.
the boss made us work 12 hours a day.
we were made to work 12 hours a day.
(5) 主語從句中有動詞do,后面作表語的不定式的 to可帶可不帶。
all we can do now is (to) wait.
(6) find 當“發現”講時，后面作賓語補足語的不定式符號to可帶可不帶。
we found him (to) work very hard at the experiment.
但如果是不定式 to be，則不能省略。
she found him to be dishonest.
4) 連詞if在部分虛擬條件句中可省略，但后面的語序有變化。
had they time, they would certainly come and help us.
(2) were i you, i would do the work better.
(3) should there be a flood, what should we do?
5) 主句和從句各有一些成分省略。
the sooner (you do it), the better (it will be).
step 3: homework
finish all the exercises about “ellipsis” in your book.
附錄一 背景資料 (background knowledge)
1 .volcanoes
there are thousands of volcanoes allover the world. what makes volcanoes? what happens?
the inside of the earth is very hot. because it is very，very hot，the rock has melted like ice. it has become liquid，like water. it is always boiling，like water in a kettle. if you have seen a kettle boiling，you know that the steam and boiling water try to get out. the very hot melted rock inside the earth also tries to get out. usually it cannot because the outside of the earth is too thick and strong.
but in some places the outside of the earth is thin and weak. sometimes a crack（a small opening）appears. the hot melted rock .which we call“lava”，pushes up through the crack and bursts through. steam and gas shoot up into the air and the hot melted lava pours out. big pieces of rock may be thrown high into the air.
after a while the volcano becomes quiet again. the melted lava becomes hard. later the same thing happens again and again. each time more hot lava pours out on top of the cold lava and then becomes hard. in this way a kind of mountain is built up，with a hole down the middle. perhaps the volcano will then be quiet and no more lava will burst out. perhaps it will start again hundreds of years later.