Question

which sentence uses pertinacious correctly?
the medicine was so pertinacious that it immediately cured his headache and allowed him to return to work within minutes.
the pertinacious investigative reporter spent three years tracking down the lead, despite numerous legal threats and dead ends.
she felt pertinacious when she realized she had accidentally left her umbrella on the bus during a torrential downpour.
the teacher gave a pertinacious lecture on the history of the roman empire, making it so brief and lighthearted that the students forgot the main points.

Explanation:

To determine the correct usage of "pertinacious", we first define the word: "pertinacious" means holding firmly to a course of action, opinion, etc., stubbornly persistent.

• For the first sentence: A medicine curing a headache quickly does not relate to being persistent, so this is incorrect.
• For the second sentence: An investigative reporter spending three years tracking a lead despite threats and dead ends shows persistent effort, which matches "pertinacious".
• For the third sentence: Forgetting an umbrella in the rain would likely lead to feelings like frustration, not persistence, so this is incorrect.
• For the fourth sentence: A brief and light - hearted lecture is not consistent with the meaning of "pertinacious" (which implies persistence, not brevity or light - heartedness), so this is incorrect.

Answer:

The pertinacious investigative reporter spent three years tracking down the lead, despite numerous legal threats and dead ends.