用来表示省略事件的事故树符号是（）

A．矩形符号

B．圆形符号

C．屋形符号

D．菱形符号

When a driver is suspected of having had too much to drink, testing the driver’s ability to walk a straight line gives a more reliable indication of fitness to drive than does testing the driver’s blood-alcohol level.
Which of the following, if true, best supports the claim made in the statement above

A．Not all observers will agree whether or not an individual has succeeded in walking a straight line.

B．Because of genetic differences and variations in acquired tolerance to alcohol, some individuals suffer more serious motor impairment from a given high blood-alcohol level than do others.

C．Tests designed to measure blood-alcohol levels are accurate, inexpensive, and easy to administer.

D．More than half the drivers involved in fatal accidents have blood-alcohol levels that exceed the legal limit, whereas in less-serious accidents the proportion of legally intoxicated drivers is lower.

E．(E) Some individuals with high blood-alcohol levels are capable of walking a straight line but are not capable of driving safely.