What drawbacks initially prevented the widespread acceptance and use of Opportunistic Key Caching (OKC)?

A.
Sharing cached keys between controllers during inter-controller roaming created vulnerabilities that exposed the keys to attackers.

B.
Because OKC is not defined by any standards or certification body, client support was delayed and sporadic early on.

C.
Key exchanges during fast roams required processor-intensive cryptography, which was prohibitive for legacy devices supporting only TKIP.

D.
The Wi-Fi Alliance continually delayed the creation of a client certification for OKC, even though it was defined by IEEE 802.11r.