Choice "A" is correct. The act of "perfection" of a security interest establishes a priority over claims of most subsequent secured creditors.
Choice "c" is incorrect. In many cases the act of "perfection" requires the filing of a financing statement.
Choice "b" is incorrect. The act of "perfection" does not necessarily give the secured party a priority over all other parties (e.g., buyers of inventory in the ordinary course of business have superior rights). (Again, watch out for all inclusive words such as "all.")
Choice "d" is incorrect. In most cases the secured party (creditor) obtains "perfection" while the debtor possesses the collateral.