1.What’s the (3 letters)of this experiment?
2.We use (11 letters)to provide power for machines.
3.It is time for us human beings to take measures to protect all living things to keep the (7 letters)of nature.
4.We students should go to bed early and get up early to (4 letters)a good habit.
5.Both teachers and students in our school are deeply impressed by Professor Smith’s
(7 letters).