What statements about ERP slot times are true?

A.
When the ERP-OFDM modulation is in use, the SIFS and slot time are always equal.

B.
When HR-DSSS is in use in an ERP BSS, a slot time consists of a Rx-to-Tx turnaround time and an energy detect time totaling 20 .

C.
All interframe spaces are calculated based on the slot time value.

D.
The optional 9 slot time may not be used if the BSS has one or more associated non-ERP stations.

E.
When the ERP DSSS-OFDM modulation is in use, all stations may use the 9 slot time.