Which type of DSL attains downstream and upstream speeds of 1.544 Mbps over two copper twisted pairs?

Which type of DSL attains downstream and upstream speeds of 1.544 Mbps over two copper twisted pairs?

A.
HDSL

B.
SDSL

C.
ADSL

D.
VDSL

Explanation:
High-rate digital subscriber line (HDSL) delivers 1.544 Mbps of
bandwidth each way over two copper twisted pairs. SDSL also delivers 1.544 Mbps but
over a single copper twisted pair. ADSL and VDSL offer a higher bandwidth downstream
than upstream.