Question:
A series of injections are used to battle a type of cancer in patients, but they do not always provide a hundred percent success rate.

Who is they referring to in this sentence?
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Answer:
A series of injections

Question:
The boy lent his friend a pencil because the teacher told him to share.

Who is him referring to in this sentence?
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Answer:
The boy

Question:
John gave a large sum of money to Bill because he needed a loan.

Who is he referring to in this sentence?
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Answer:
Bill

Question:
Apple indicated that the Siri program would not be available for previous IPhones because they do not have the capabilities to run such a program.

Who is they referring to in this sentence?
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Answer:
previous IPhones