Answer:
Here, h represents the hours.
As per the statement:
Ursula earns $9 per hour.
In 1 hour Ursula earns = $9
then;
in h hours Ursula earn = 9h
Therefore, an expression which tells that 9h money Ursula earns for h hours.
Sarah expression 9h is correct.
Because it tells how much money she earns each hours.