30.According to the passage,the invention of the visible-light microscope allowed scientists to

(A)see viruses directly

(B)develop the electron microscope later on

(C)understand more about the distribution of the chemical elements

(D)discover single celled plants and animals they had never seen before.

31.The word "minuscule"in line 5is closest in meaning to

(A)circular

(B)dangerous

(C)complex

(D)tiny

32.The word "it"in line 7refers to

(A)a type of microscope

(B)human perception

(C)the natural world

(D)light

33.Why does the another mention me visible light microscope in the first paragraph?

(A)To begin a discussion of sixteenth century discoveries.

(B)To put the x-ray microscope in historical perspective

(C)To show how limited its uses are

(D)To explain how it functioned

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.

35.The word "enables"in line 32is closest in meaning to

(A)constitutes

(B)specifies

(C)expands

(D)allows