Low beams do not work, high beams do

1997 mercury sable - low beams do not work, high beams do. Seems turn signal switch was intermittent before lights stopped working. Alternator was recently replaced. Is this the bulbs or a switch?

it seemed to me to be the turn signal switch that responded to movement before the low beams quit. The other lights all work, including the high beams when I hold the turn signal lever back while driving.