In order to determine the age of ancient pottery, archaeologists often rely on a technique called thermoluminescence dating. This method measures the accumulated radiation dose of the time elapsed since the material _____ heated in a kiln.
Which choice completes the text so that it conforms to the conventions of Standard English?
Explanation
Context: The method measures "the time elapsed since the material ___ heated in a kiln" — the firing is a completed event in the distant past.
Answer: A) was last
Why? "Since" + a finished past event takes simple past: "since the material was last heated."
Traps:
- B) is last → present tense for an ancient, completed firing.
- C) has been last → present perfect implies heating continuing up to now; the firing ended long ago.
- D) to be last → infinitive; leaves the "since" clause without a finite verb.