The ancients had many ingenious methods for measuring time. Water clocks, for example, were used in ancient Greek and Rome to time orators speeches. One version comprised pouring water time. As with water clocks, sundials needed to be calibrated in order to show the passage of time. Prior to the development of sundials, stones or poles could be placed m the ground. In addition to their water clocks and sundials, the ancient Egyptians used obelisks and pyramads to tell the time from the passage of the sun.

Question: The passage states that the ancient Egyptians built obelisks for telling the time.
Options:
A. true, B. false, C. uncertain
Answer: "B"