A.1
B.2
C.4
D.3

A.4,68.
B.5,64.
C.3,24.
D.4,00.

A.HCl loãng, nóng.
B.HNO3 đặc, nóng.
C.HNO3 loãng, nóng.
D.H2SO4 đặc, nguội.

A.CrO3.
B.CrO.
C.Cr2O3.
D.K2CrO4.

A.investigations
B.microscopes
C.properties
D.X-rays

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

A.To explain how it functioned
B.To show how limited its uses are
C.To begin a discussion of sixteenth century discoveries
D.To put the X-ray microscope in historical perspective

A.complex
B.tiny
C.circular
D.dangerous

A.understand more about the distribution of the chemical elements
B.develop the electron microscope later on
C.discover single-celled plants and animals they had never seen before
D.see viruses directly

A.Sources of illumination for microscopes
B.The detail seen through a microscope
C.Outdated microscopic technique
D.A new kind of microscope