A is correct for me : "Although Shared Key authentication might seem to be a more secure solution than Open System Authentication, in reality Shared Key could be the bigger security risk". You can refer to p.731 of Study Guide (6th Edition) for the full quote.

'802.11 authentication is either Open System Authentication or Shared Key Authentication. Shared Key Authentication is deprecated in the standard and is not secure. It should never be used today. Open System Authentication is performed before either Pre-Shared Key or 802.1X/EAP authentication.' Official Book CH 7

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I would say B Open system Authentication