To deploy Cisco WSA in transparent mode, the configuration component that must be used is WCCP on switch. WCCP stands for Web Cache Communication Protocol, which is a protocol that allows a network device (such as a switch) to redirect web traffic to a proxy server (such as Cisco WSA) transparently. This means that the client does not need to configure any proxy settings on the browser, and the proxy server can intercept and process the web requests and responses without the client’s knowledge. WCCP can also provide load balancing and failover capabilities for multiple proxy servers.

The other options are incorrect because they are not required or relevant for transparent mode deployment. Option A is incorrect because MDA (Multilink PPP Dial Access) is a feature that allows multiple physical links to be aggregated into a single logical link for dial-up connections. It has nothing to do with transparent mode. Option B is incorrect because PBR (Policy-Based Routing) is a feature that allows routing decisions to be based on criteria other than the destination IP address, such as source IP address, protocol, port, etc. It is not necessary for transparent mode, as WCCP can handle the traffic redirection. Option D is incorrect because DNS resolution on Cisco WSA is not a configuration component, but a function that allows the proxy server to resolve domain names to IP addresses. It is not specific to transparent mode, as it is also used in explicit mode. References:

What is the difference between transparent and forward proxy mode?

User Guide for AsyncOS 12.7 for Cisco Web Security Appliances - LD (Limited Deployment) - Acquire End-User Credentials

Cisco WSA : Is it possible to use web proxy in transparent mode without WCCP?