[ a, an, the, Zero Article ]
Roentgen was ___ German physicist who discovered x-rays, revolutionizing medical diagnosis.
a. a
b. an
c. the
d. X [Nothing]

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Grammar of Future Planstake, make, doGrammar and VocabulariesZero Conditional SentencePast Tense vs Present TenseConditionals and Modal VerbsPreposition of PlaceAdjectives and DegreesToeic VerbSimple Past TensesOther quiz:
Vocabulary › ViewQuiet! Everyone needs to ____________ and _______ so that we can work together.
A. carry on, rest
B. put your feet up, join in
C. go off, stay
D. take five, relax
Grammar › View
I am_____a car.
A. not rich enough to buy
B. too rich enough to buy
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so rich to buy
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A. Reserved
B. Chatty
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Tenses › View
I think that they _____ (arrive) tomorrow morning.
A. will arrive
B. arrive