What are valid device types of concurrent SRDF? 06/02/2017 – by Mod_GuideK 0 What are valid device types of concurrent SRDF? A. R11 R22 R21 B. R11 R12 R22 C. R12 R21 R22 D. R11 R12 R21 SHOW ANSWERSCorrect Answer: A Explanation/Reference: Download Printable PDF. VALID exam to help you PASS.