Which four of the following statements about LDNS probes are true? (Choose four.)
- Only GTM devices can act as a prober.
- They check each requesting LDNS that has made a request of the GTM.
- They can determine available cache size on the client.
- They are used to develop path metrics.
- They verify the link between a data center and an LDNS.
- Probing only takes place if GTM is configured to use dynamic load balancing.