-Is air the lightest thing in the world?-Not ＿.Scientists fr

英语翻译
The early universe contained only the lightest elements,hydrogen and helium.Heavier elements,such as carbon,form only in nuclear reactions in stars and are dispersed when the stars explode.A recently discovered gas cloud contained carbon several billion years ago,when the universe was no more than two billion years old.
　　If the statements above are true,which of the following must,on the basis of them,also be true?
　　（A）The earliest stars contained only hydrogen.
　　（B）Some stars were formed before the universe was two billion years old.
　　（C）The carbon in the gas cloud later formed part of some stars.
　　（D）No stars identified to date are as old as the gas cloud.
　　（E）The gas cloud also contained hydrogen and helium.

It is known that hydrogen _______ the lightest element.
1 be
2 was
3 has been
4 is

-- Is air the lightest thing in the world? -- Not . Scientists from Zhejiang University have just developed the world’s lightest material. A．now B．yet C．then D．again

The weightof an object will be the lightest when it is put at ( ).
A.the North Pole B.the Soth Pole C.the Equator D. the center of the Earth
说明原因
答得好我会给悬赏分,一定.
谢谢

Hydrogen is the lightest element with an atomic weight of 1.008 翻译这句。

not-in the lightest,drop by someplace,come up in school exams,found by accident,have the light
一点儿也不,顺便到访某处,在学校测试中名列前茅,被人们意外发现,灯一直亮着.
辅导书上说的,我全部都没看过.