Surveys indicate that 52 percent of all women aged eighteen to sixty-five are in the labor force (employed outside the home) in any given month. On the basis of these surveys, a market researcher concluded that 48 percent of all women aged eighteen to sixty-five are full-time homemakers year-round.
Which of the following, if true, would most seriously weaken the researcher’s conclusion

A．More women are in the labor force today than during any other period since the Second World War.

B．Many workers, both men and women, enter and exit the labor force frequently.

C．Although only a small sample of the total population is surveyed each month, these samples have been found to be a reliable indicator of total monthly employment.

D．Surveys show that more women than ever before consider having a rewarding job an important priority.

E．(E) Women who are in the labor force have more discretionary income available to them than do women who are not.

列车信号机平时在关闭状态时，其允许灯光的主灯丝断丝会报警吗？为什么？何时才能报警？