This is because:

* DNA is antiparallel, meaning the two strands run in opposite directions. One strand runs 5' to 3', and the other runs 3' to 5'.

* RNA polymerase synthesizes RNA in the 5' to 3' direction.

* To create a new RNA strand in the 5' to 3' direction, RNA polymerase must read the template DNA strand in the 3' to 5' direction.

This ensures that the newly synthesized RNA strand is complementary to the template DNA strand.