题目内容：

WASHINGTON---At least four more U.S. air-traffic controllers are caught nodding off on the job at three separate airports across the nation, the government said Wednesday.

The controller working alone in the tower fell asleep and was out of communication for 16 minutes while a medical flight carrying a patient was trying to land at about 2 A.M. Wednesday at Reno-Tahoe International Airport in Nevada, the Federal Aviation Administration (FAA) said in a statement.

The FAA announced that it is also investigating a controller who fell asleep Monday at Boeing King County International Airport in Seattle and two controllers who were unresponsive at McGhee Tyson Airport in Knoxville, Tennessee on Feb.19.

“I am sick of this,” Senate Commerce, Science and Transportation Chairman Jay Rockefeller, a West Virginia Democrat, said in a statement. “We can’t have a system where some of the people responsible for safety are asleep at the switch.”

As the incidents pile up, sleep experts say it demonstrates that the agency faces a systemic issue with the thousands of people expected to work through the night in safety-critical jobs. Scientific research shows that workers on midnight shifts make more errors because it is so difficult for the body to adapt to sleeping during the day, they say.

The agency will add an extra controller at the 27 towers staffed with one worker on the midnight shift, the FAA statement said.

Representative John Mica, the Florida Republican who chairs the House transportation committee, criticized the decision to add controllers. “Only in the federal government would you double up on workers, averaging $161,000 per year in salary and benefits, that aren’t doing their job,” Mica said in a statement. Mica has pushed legislation that would allow as many as 90 smaller airports to switch from federal to private controllers.

“People have known these problems with fatigue（疲劳）have existed for years,” said John Goglia, a Boston-based aviation safety consultant. “They’re now showing up. The FAA is admitting they exist. Now the FAA needs to work on it.”

The four controllers in Nevada, Seattle and Texas have been suspended(暂时停职) during the investigations, the FAA said.

1.The underlined part “double up on workers” means “______”.

A．add two more workers	B．staff two workers at a post
C．settle two workers in a double room	D．give the workers double pay

2.According to John Goglia, fatigue problem ______.

A．is a known potential danger	B．has never appeared before
C．is common for day-time shift workers	D．seldom shows up at night

3.Which statement is true?

A．A controller fell asleep without communication for 16 minutes in Knoxville, Tennessee.

B．A medical flight carrying a patient failed to land with the controller asleep.

C．Jay Rockefeller pays little attention to sleeping at the switch.

D．Mica refused to support the decision to staff more controllers on the midnight shift.

4.We can infer from the passage that ______.

A．All the controllers in the US were working alone while they were on duty

B．The incidents are rooted in fatigue problems and those on midnight shifts need an extra nap

C．In the U.S. , thousands of people expect to work through the night in safety-critical jobs

D．The agency has added an extra controller at the 27 towers