On December 21st, just in time for the seasonal festivities, the Bush administration raise

d the terror alert from "elevated" to "high". This is the fifth time that the alert has been raised to "code orange"—but it looks as if it could be kept at this level for quite some time. Officials seemed to be more nervous than usual, since unlike previous decisions to raise the threat level, this one was apparently unanimous among officials in the United States Department of Defense. Asked whether the alert was "truly serious", Donald Rumsfeld, the defense secretary, replied "yes, you bet your life".

The authorities have noticed a marked increase in "chatter". They have also picked up specific threats— some of them, it seems, to do with hijacking aircraft and crashing them into buildings. The targets reportedly included some big cities, for example, Las Vegas is a particular worry, but more obscure places were also chattered about, including Rappahannock County, or perhaps the town of Tappahannock, both in rural Virginia, and Valdez, in Alaska. The point of any such terrorism would be to make sure that no American anywhere felt safe.

A particular focus of concern has been flights from abroad. Air France canceled six flights between Paris and Los Angeles at American government's request. French authorities questioned and released a dozen or so passengers but several people with tickets, including one who was reportedly a trained pilot, failed to turn up for the flight. On December 29th some international airlines were ordered to place armed air marshals on flights over the United States.

On top of all this, there have also been more familiar signs of security being beefed up at nuclear plants, ports and other possible targets. Surface-to-air missiles have once again been conspicuously deployed in Washington, DC.

Inevitably, some people have begun to question whether putting the country on such a high state of readiness is worth it. The process costs about $1 billion a week. Critics worry that people will become unconcerned about repeated security alerts. They also complain about the government sending mixed signals: telling Americans they are in great jeopardy(危险) but also that they should go about their business as normal. However, the critics may be too fussy(挑剔的). It is extremely hard to see what else the government could have done without either ignoring credible threats or creating mass panic. This may be the only way to face the possible threats.

Why did officials appear more worried about the terror alert this time？

A．Because the raise of terror alert was in the seasonal festivities this time.

B．Because it was the fifth time to raise the terror alert to code orange.

C．Because terror alert would be kept at this level for a period of time.

D．Because officials in the Department of Defense all agreed on the decision.