On a bookshelf there are 50 mathematics and physics books. No two physics books stand side by side, but every mathematics book has a mathematics book next to it.  What is the least possible number 
选项为:A:The number of mathematics books is at least 32.  B:The number of physics books is at most 17.  C:There are 3 mathematics books standing together.  D:If the number of physics books is 17, then one of them is the first or the last on the shelf.  E:Among any 9 consecutive books, at least 6 are mathematics books.  请回答其中一个选项.