Why do big American companies demand that their employees pass in and out of their work place with an access card?

A. Because they want to figure out a way to hold the terrorists.
Because they feel threatened and want to keep outsiders away.
C. Because they think it is a symbol of their identity.
D. Because it is more convenient.

Businessmen are buying new machines to analyze a ________ in order to tell whether their friend or client is _________ .

People think that electronic X-ray equipment can hold ___________at bay.

Airports are still a place of education and fun today.

A. 对
B. 错