GMAT Sentence Correction (SC) | Sentence Correction basic identification

Q. Because they were eye witnesses to the crime,Amy, Sue and Jack were called to testify at the robbery hearing .

a) Amy, Sue and Jack were called to testify at the robbery hearing
b) Amy, Sue and Jack they were called to testify at the robbery hearing
c) Amy, Sue and Jack was called to testify at the robbery hearing
d) Amy, Sue and Jack were calling to testify at the robbery hearing
e) Amy, Sue and Jack were called to testifying at the robbery hearing

I know this is an easy question. But the
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