______ , the experimental treatment showed promising results in early clinical trials, though long-term effects remain unknown.
Which choice completes the text so that it conforms to the conventions of Standard English?
- A
Being developed by researchers nearly a decade ago
- Bcheck_circle
Developed by a small team of researchers
- C
Developing it for nearly a decade
- D
Having developed it for nearly a decade
Explanation
Past participle "Developed" correctly modifies the subject "treatment" (the treatment was developed). The other options either dangle or are awkward.