some SC questions,pls help me!

britney_gao

1 The Van de Graaff generator, an electrostatic machine used of nuclear physics to study transformations in subatomic particles, produces powerful electric currents.
which one is wrong? how correct it?

2 observation of the sun, moon, and stars has enabled humans to determine both the seasons and the time from day.
which one is wrong? how to correct it?

3 the hardness of mineral often gives a clue to its identity.
i think maybe "to" should be changed to "of", but it is not right. the key is "of mineral". i can not understand. so why is it wrong? and how to correct it?


3x

困难是弹簧

久了没碰题了，欢迎讨论！

1、of --->in
2 from -->of
3 mineral--->minerals
对于第三个是他们的习惯。可数名词单独使用，在一般情况下，要么前面有限定词，要么用复数。