34. Why did it take so long to develop the x-ray microscope?
(A) Funds for research were insufficient.
(B) The source of illumination was not bright enough until recently.
(C) Materials used to manufacture x-ray tubes were difficult to obtain
(D) X-ray microscopes were too complicated to operate.
答案:登入後查看
統計: A(2), B(5), C(2), D(0), E(0) #803122
統計: A(2), B(5), C(2), D(0), E(0) #803122