Indefinite articles are commonly used in English to refer to non-specific singular nouns. Their correct use depends not only on spelling, but also on the initial sound of the following word. In academic and professional communication, the accurate use of indefinite articles contributes to grammatical precision and clarity. Read the statements below carefully:
I.The researcher adopted a innovative strategy during the final stage of the experiment.
II.The student bought an umbrella before attending the international conference.
III.The company hired a European consultant to supervise the financial department.
IV.The professor delivered an university lecture about language acquisition theories.
V.The engineer described a one-story building during the urban planning presentation.

Identify in which statements there is the correct employment of indefinite articles according to standard English grammar.