YDS NOUN CLAUSES / TEST 3 21. Soru

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100 %

21.

- For the last few weeks, medical teams
......... day and night in an effort to find
out exactly what ......... this terrible
illness, but they've had little success so
far.

are working/will cause

have worked/will have caused

have been working/is causing

will have worked/will be caused

were working/had been caused

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