Which of the following is the probable title of the passage

A．absolutely safe at low levels
B．very efficient for cooking
C．cancer-causing iii people with weak eyes
D．completely understood by scientists

A．Since 1866, use of the metric system in the U.S. has been increasing.
B．Since 1988, the metric system has been the preferred system of weights and measures for U.S. trade and life.
C．In 1988, Congress passed a law to prevent the use of the Customary System in trade and commerce.
D．On Dec. 23, 1975, Pres. Gerald R. Ford signed the Metric Conversion Act of 1975 to adopt the metric system in the U. S.