【单选题】

As Texas begins to recover from two weeks of devastating storms, a generally hidden truth about its economy will come to light again. Most of the builders and electricians who will have to repair the houses, remake the roads and re-establish the electrical power lines will have to take on undocumented workers in order to meet their contracts. In 1996 the Immigration and Naturalisation Service (INS) conservatively estimated that Texas had over 600,000 undocumented immigrants doing the jobs no one else wants: hauling carcasses in packing plants, picking fruit, cleaning hotel rooms, or sorting out the unspeakable damage caused by natural disasters.

Mention the issue of these workers to a Texan, and he is liable to fall uncharacteristically silent.Even state legislators avoid the issue. They know that many of their constituents employ undocumented workers. They also know that the booming Texas economy is driven in part by the ready supply of cheap, diligent, illegal labour.
Dallas is one magnet for undocumented workers. The city’s politicians oppose INS crackdowns fearing they will damage the local economy and bankrupt small companies. Houston is another. There a dawn drive past some of the city’s 36 informal day-labour sites shows the size of the undocumented workforce. Young Mexicans wait on the pavement, ready to jump into the back of any pick-up truck that slows down to take them. Houston police estimate that over 150,000 labourers, about 85% of them undocumented, gather every day in search of a joB、It is a testament to the vitality of the Texas economy that most of them get hired usually to mix cement and shift bricks. No questions are asked, no papers signeD、Most workers do not even know their employer’s name. They are paid in cash, around 40 dollars a day while the averageAmerican earns more than twice as much.
According to the passage, the presence of immigrant workers in Texas ______.
A、is seen as a problem by local authorities
B．is tolerated given that it helps the local economy
C．can be considered evidence of the failing economy
D．is a source of racial conflict