The original sentence is -
The electron cloud model was conceived by Richard Feynman in an attempt to accurately depict the probability density of an electron as
it occupies the space surrounding the nucleus of an atom or molecule.
Meaning: The actual sentence implies that the model was conceived (by Richard) .
Note that the emphasis is not on doer but on the model. The intention was clear - to accurately depict the probability density of an electron. Now, let's see the choices.
A. The electron cloud model was conceived by Richard Feynman in an attempt to accurately depict the probability density of an electron as it occupies the space surrounding the nucleus of an atom or molecule
The pronoun "it" clearly refers to the electron.
Why? Because "model" and "density" can't occupy the space.
There is no grammatical error. Hold on with it.B. The electron cloud model was
conceived from Richard Feynman in an attempt to accurately depict the probability density of electrons as
they occupy the space surrounding the nucleus of an atom or molecule
"they" can refer to "electrons" . However, "conceived from" is idiomatically incorrect. C. In an attempt to accurately depict the probability density of electron as it occupies the
space that surrounds the nucleus of an atom or molecule, Richard Feynman conceived the electron cloud model
Note: Let's understand the the difference in the meaning
1. space surrounding the nucleus = talks about the space around the nucleus. --- ok
2. space that surrounds the nucleus = space is the doer. The space acts <something> to be around the nucleus. --- This is nonsensical. D. For an attempt to accurately depict the probability density of an electron as it occupies the space surrounding the nucleus of an atom or molecule, Richard Feynman conceived the electron cloud model
An attempt is "intentional" to infinitive form is better. (i.e. To attempt).
The emphasis is shifted from the model (as in original sentence) to the doer of the sentence i.e. Richard Feynman.
Shift in meaning. E. In an attempt to
depict accurate the probability density of an electron as it occupies the space surrounding the nucleus of an atom or molecule, Richard Feynman conceived the electron cloud model
"depict" is a verb. To modify it, we need an adverb (i.e. accurately) and not an adjective. Thus, choice
A is the best construction.