I saw thousands of peple enter the room ___crowds ,为什么 in crowd 不行,两者有何区别

I saw thousands of peple enter the room ___crowds ,为什么 in crowd 不行,两者有何区别 I saw ___ books in our school library.A.thousand and hundred of B.thousands and hundred of C.thousand and hundreds of D.thousands of huandreds of请问应该选哪一个? thousands of thousands是什么意思 thousands of thousands of thousands of. thousand 、thousands、thousands of区别 I saw saw saw thousands of tens of thousands of hundreds of thousands of Tens of thousands of hundreds of thousands of thousands and thousands of 和thousands of的区别 thousands and thousands of与thousands of的区别? tens and thousands of thousands of people Hundreds of thousands tens of thousands tens