A.as soon as
B.provided
C.so that
D.already

A.surpassed
B.overtaken
C.exceeded
D.outdone

A.example
B.understanding
C.clarification
D.explanation

A.lost
B.missing
C.absent
D.misplaced

A.lost
B.missing
C.absent
D.misplaced

A.retreat
B.conquer
C.gather
D.remain

A.They will eventually change the illumination range that they now use
B.They will provide information not available from other kinds of microscopes.
C.They will eventually be much cheaper to produce than they are now.
D.They will probably replace electron microscopes altogether.

A.Apples are not as good as people may think.
B.Eating an apple in the morning proves beneficial.
C.Pectin can cause digestive problems at night.
D.Flavonoids are as good as beta carotene.

A.Apples are not as good as people may think.
B.Eating an apple in the morning proves beneficial.
C.Pectin can cause digestive problems at night.
D.Flavonoids are as good as beta carotene.

A.Ag+.
B.Mg2+.
C.Na+.
D.Cu2+.