how do you achieve this?

You are loading a file into a database but the file name is unknown at design time and will
have to be passed dynamically to a Package at run time; how do you achieve this?

A.
Create a variable, use it in Topology at the File dataserver-level, and add it to a package
as a Declare Variable step

B.
Create a variable, use it in Topology at the File dataserver-level, and add it to a package
as a Set Variable step

C.
Create a variable, use it as the Resource Name of the File datastore, and add it to a
package as a Declare Variable step

D.
Create a variable, use it as the Resource Name of the File datastore, and add it to a

package as a Set Variable step