I want to test the ability of students to read a passage and answer questions about it. Could you please come up with a good question for the passage "On March 10, 1876, three days after his patent was issued, Bell succeeded in getting his telephone to work, using a liquid transmitter similar to Gray's design. Vibration of the diaphragm caused a needle to vibrate in the water, varying the electrical resistance in the circuit. When Bell spoke the famous sentence "Mr. Watson—Come here—I want to see you" into the liquid transmitter, Watson, listening at the receiving end in an adjoining room, heard the words clearly."? 

What did Bell create?