a question on bitcoin transaction I would like to know whether these statements are true.

"Say a Bitcoin market participant should choose to sell a large volume of the currency. Because each transaction is broadcast to a network that is — by design and necessity — public and publicly observable, the entire market could become privy to such an event."
The public network would see only that a transaction occurred - that a large amount of Bitcoin was transferred from one address (or set of addresses) to another.  There wouldn't be any way to be sure, from that information alone, that the transaction was actually a sale, rather than the same owner just moving the coins to a different address (e.g. for cold storage).  One also couldn't necessarily know who the owner or recipient of the coins was.  If the coins were spread across many addresses, you couldn't even be sure they all belonged to the same person.

So I'd say that statement is false.