You need to ensure that all search requests are processed by Server2 only

You have a SharePoint Server 2010 Service Pack 1 (SP1) server farm. The server farm contains two
Web servers named Server1 and Server2. Server1 and Server2 are configured as query servers. You
need to ensure that all search requests are processed by Server2 only. What should you do from
Central Administration?

A.
Modify the Service Application Associations settings.

B.
Create a new Search service Application.

C.
Modify the Host Distribution Rules settings.

D.
Modify the Search Application Topology settings.

Explanation:
Host Distribution Rules settings:
Used for crawling not query
Service Application Association settings

Used to associate a service to a webapplication
Search Application topology settings
Used to changed topology settings like changed components and select servers as failover-only
query components.
Create a new search service application to much overhead.
Ref: http://technet.microsoft.com/en-us/library/ee805955.aspx