D. are thought of as generous if they tip 15%.
5. The author thinks that ____.
A. tipping can benefit greatly a country’s economic growth.
B. tipping can ensure the quality of service a customer receives.
C. tipping can improve a country’s cultural environment.
D. tipping is not conductive tertiary industry.
Text 2
When he died in April of 1993, Dr. Jeol Hiderbrand was 101 years old, had been married for seventy years, and had taught freshmen chemistry to over 40,000 students. In addition, he had published a popular textbook and dozens of articles, had managed the U. S. Olympic ski team, and had discovered a way to allow deep-sea divers to stay underwater longer. In his own way, Dr. Jeol Hiderbrand was certainly a genius.
During that time, Dr. Jeol Hiderbrand discovered that the gas helium could be combined with oxygen for use as diving gas to allow divers to dive deeper and take the great pressure of the water without the physical discomforts that had been experienced when they used another gas, nitrogen. The use of helium for deep-sea diving is now standard practice.