O got this all wrong on my mock but here is how I would solve it re looking at each of the questions..
Studying the fruit fly,
a household nuisance but a time-honored experimental subject, has enabled the secrets of how embryos develop to begin to be unraveled by scientists.
approach - cancel -, a household nuisance but a time-honored experimental subject, - which now leaves us with
Studying the fruit fly has enabled the secrets of how embryos develop to begin to be unraveled by scientists.
Meaning. Scientist have studied FF which enables them to understand the secret of how embryos develop
Problems in the original sentence
- The subject is scientist right at the end
- The study has enabled the scientist to unravel secrets
- how embryos develop to begin
(A) Studying the fruit fly, a household nuisance but a time-honored experimental subject, has enabled the secrets of how embryos develop to begin to be unraveled by scientists.
because of the above reason a is out(B) By the study of the fruit fly, a household nuisance and also a time-honored experimental subject, it was possible for the secrets of how embryos develop to begin to be unraveled by scientists.
same reason as above "how embryos develop to begin to be" + "by the study of" puts the entire sentence into the past tense(C) By studying a household nuisance but a time-honored experimental subject, the fruit fly enabled scientists to begin to unravel the secrets of how embryos develop.
"by the study of" puts the entire sentence into the past tense + the comma has been removed at the start (D) By studying the fruit fly, a household nuisance and also a time-honored experimental subject, the secrets of how embryos develop are beginning to be unraveled by scientists.
originally I chose this but once I re-studied it I realised
"by the study of" puts the entire sentence into the past tense + beginning makes it past tense but the original sentence is present tence (E) The study of the fruit fly, a household nuisance but a time-honored experimental subject, has enabled scientists to begin to unravel the secrets of how embryos develop.
right answer
- present tense
- remove the ing a red light always to re-evaluate the answer
- correct the awkward part of "how embryos develop to begin"