In his eleventh-century treatise *Book of Optics*, polymath Ibn al-Haytham demonstrated that light travels in straight lines through his experiments with a dark chamber, or camera obscura. Although earlier scholars ______ similar optical phenomena, al-Haytham was the first to provide a systematic, mathematical explanation of how light rays project inverted images onto a screen.
Which choice completes the text so that it conforms to the conventions of Standard English?
- Aobserve
- Bhave observed
- had observedCevap
- Dwill observe
Cevap
had observed
The past perfect verb 'had observed' is correct because the passage describes events that occurred in the past (using the past tense verbs 'demonstrated' and 'was'). Since the actions of the 'earlier scholars' occurred before Ibn al-Haytham's eleventh-century discoveries, the past perfect tense is required to establish the correct temporal order of these past events.
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Anahtar Kavram
Verb Tense, Aspect, and Mood