A DMT DSL modem is working on a “shared line” with standard telephone service (POTS). When the subscriber picks up the telephone handset, the DSL modem untrains, then retrains at a lower DSL line rate. When the telephone is not off-hook, the DSL modem will train at the subscribed rate (normal operation).Which of the following is the probable cause of this symptom?

A.
An improper DSL line rate was provisioned for shared lines.

B.
A microfilter or splitter was not correctly installed between the telephone and the line.

C.
The noise level on the telephone line will not allow DSL and POTS voice at the same time.

D.
An incorrect DMT operating mode was provisioned in the DSLAM.