恳请大家帮忙解答几道CR题

1、Generally scientists enter their field with the goal of doing important new research and accept as their colleagues those with similar motivation. Therefore, when any sicentist wins renown as an expounder of science to general audiences, most other scientists conclue that this popularizer should no longer be regarded as a true colleague.

the explanation offered above for the low esteem in which scientific popularizers are held by reserach scientists assumes that

A.serious scientific research is not a solitary activity, but relies on active cooperation among a group of colleagues

B.research scientist tend not to regard as colleagues those scientists whose renown they envy

C.a scientist can become a famous popularizer without having completed any important research

D research scientists believe that those who are well known as popularizers of science are not motivated to do important new research

Eno important new research can be accessibel to or accurately assessed by those who are not themselves scientists

答案为D，能否给个详尽点的解释呢？

2、 A proposed change to federal income tax laws would eliminate deductions from taxable income for donations a taxpayer has made to charitable and educational institutions. iF this change were adopted, wealthy individuals would no longer be permitted such deductions. THerefore, many charitable and educational insitutions would have to close their doors.

A. without the incentives offered by federal income tax laws. at least some wealthy individuals would not donate as much money to charitable and educational insitutions as they otherwise would have.

B.Money contributed by individuals who make their donations because of provisions in teh federal tax laws provides the only source of funding for many charitable and educational institutions.

这题的正确答案为A，那B为是么不对呢？

3、When people evade income taxes by not declaring taxable income, a vicious cycle results. Tax evasion forces lawmakers to raise income tax rates, which causes taht tax burden on nonevading taxpayers to become beavier. THis, in turn, encourages even more taxpayers to evade income taxes by hiding taxable income.

c.WHEN lawmakers establish income tax rates in order to generate a certain level of revenue, they do no t allow adequatedly for revenue that ill be lost through evasion.

这答案是什么意思?

希望同仁们帮忙解决一下好嘛》万分感激~