解析：
6. D 根据第二段和第三段，这一交易所可进行多种交易。
7. D 根据第三段，债券交易所可以进行债券和证券的交易。The security exchanges, on the other hand, are meeting places where stocks and bonds are traded.
8. D 根据第三段，The Crash of 1929 has been attributed to many causes, among them wild and unwise speculation by many people and dishonest practices on the part of some businessmen and of some members of the exchanges. 1929年的股市危机是由于许多人投机和一些商人不诚实的行为造成的。
9. A 最后一段，and in 1934, the Securities and Exchange Commission, to protect investors and the public against dishonest practice in the exchanges.政府建立的证券交易委员会使投资变得更加安全。
10. B 答案A.在文章第二段直接提到了。Some exchanges, like the Chicago Board of Trade, provide market services for several kinds of products. 答案C证券投资是不明智的和答案D买卖双方是不诚实的，这两点在文中都没有提到。
文章中指出了政府的努力来维护正常的交易秩序，暗示了政府在制止不诚实交易行为中所起的重要角色，但并没有在文中直接陈述这一点。
