Using the Present Perfect Tense

1. In the past few years, a number of states (began / have begun) to allow physician assistants and nurse practitioners to write prescriptions.

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   1. In the past few years, a number of states (began / have begun) to allow physician assistants and nurse practitioners to write prescriptions.
2. Before the changes in the laws, physician assistants and nurse practitioners (saw / have seen) patients with common illnesses.

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   2. Before the changes in the laws, physician assistants and nurse practitioners (saw / have seen) patients with common illnesses.
3. However, if the patients (needed / have needed) a prescription, a doctor had to write it.

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   3. However, if the patients (needed / have needed) a prescription, a doctor had to write it.
4. Many doctors (said / have said) that the changes are a good idea.

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   4. Many doctors (said / have said) that the changes are a good idea.
5. Physician assistants and nurse practitioners (spent / have spent) years in training by the time they get their licenses.

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   5. Physician assistants and nurse practitioners (spent / have spent) years in training by the time they get their licenses.
6. Since the new laws took effect, physician assistants and nurse practitioners (wrote / have written) many common prescriptions.

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   6. Since the new laws took effect, physician assistants and nurse practitioners (wrote / have written) many common prescriptions.
7. Recently, some people (expressed / have expressed) concern that physician assistants and nurse practitioners might make mistakes in writing prescriptions.

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   7. Recently, some people (expressed / have expressed) concern that physician assistants and nurse practitioners might make mistakes in writing prescriptions.
8. However, the possibility of a mistake in a prescription (always existed / has always existed).

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   8. However, the possibility of a mistake in a prescription (always existed / has always existed).
9. For the past several years, pharmacists (kept / have kept) track of prescription errors.

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   9. For the past several years, pharmacists (kept / have kept) track of prescription errors.
10. Doctors made all but one of the mistakes that they (found / have found) so far.

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    10. Doctors made all but one of the mistakes that they (found / have found) so far.