A verb tense question tests whether you can tell when something happens using clues in the sentence. Check that the forms fit the subject, then find the time clue near the blank. If the sentence gives a length of time and another event, ask how they fit together. Build the timeline: present forms connect to now, past forms connect to a past moment, and future forms look ahead. A long stretch of time alone doesn't tell you which tense to use.
Hints
- Hint 1
Find the time of the discovery in the words after the blank. What tense is located?
- Hint 2
Look at how for over a decade and when work together. Place the stretch of exploring in relation to the discovery.
Step-by-step
Follow the time clues
Step 1Find the event that sets the time
Start with Archaeologist Maria Sanchez: all four verb forms fit one person, so this question turns on tense, or when the exploring happens. Which event gives us a time to work from? when she finally located names a discovery that happened in the past. That makes the discovery our past moment to work from, and we now need to place her search around it.
- Step 2
Place the search on the timeline
Did the exploring begin at the discovery, or was it already going on? for over a decade says she'd spent more than ten years searching by the time she found the vessel. That long stretch describes a search continuing over time, not a new search starting at the discovery. So the exploring leads up to a later past event. Searching for a long time doesn't mean the search continues today.
- Step 3
Build the verb form
What form looks back at an ongoing search from a later past moment? The past perfect continuous does that: had points back from the past moment, and been plus an -ing verb shows the activity continuing over time. To describe the search lasting for over a decade, we put exploring after had been. That gives us had been exploring. Choice C.