Final answer:
To assist Lisa, a domain user from EMEA-CORP, in accessing a shared resource in PRACTICELABS, she should use a domain workstation lent by PRACTICELABS to sign in with her EMEA-CORP credentials.
Step-by-step explanation:
To help the visiting domain user named Lisa from EMEA-CORP access a shared resource in the PRACTICELABS parent domain, the most appropriate action among the provided options would be A: Ask the PRACTICELABS administrator to lend her a domain workstation so she can sign-in to the EMEA-CORP domain and subsequently connect to the shared resource. This is because if group nesting strategy has been set up successfully between the two domains, Lisa's permissions should allow her to access resources in the parent domain as long as she is authenticated with her own domain credentials on a system that is part of the PRACTICELABS domain.