IMO it should be D
//ism should be between TOUCH each exhibit and ACTIVATE the animated features

imskpwr wrote: In the correct option, "exhibit" and "activate" both are in a // structure. That implies, "visitors" did both the actions i.e., "Visitors activated animated functions" instead of the intended meaning that "touching an exhibit activated the animated functions.

"exhibit" is used as a Noun while "activate" is a verb; so they are not grammatically parallel.

EducationAisle wrote:

imskpwr wrote: In the correct option, "exhibit" and "activate" both are in a // structure. That implies, "visitors" did both the actions i.e., "Visitors activated animated functions" instead of the intended meaning that "touching an exhibit activated the animated functions.

"exhibit" is used as a Noun while "activate" is a verb; so they are not grammatically parallel.

Pardon,
I meant "touch" and "activate".

imskpwr wrote:"Unlike the original National Museum of Science and
Technology in Italy, where the models are encased in
glass or operated only by staff members, the Virtual
Leonardo Project, an online version of the museum,
encourages visitors to ""touch"" each exhibit, which
thereby activates the animated functions of the piece."
(A) exhibit, which thereby activates
(B) exhibit, in turn an activation of
(C) exhibit, and it will activate
(D) exhibit and thereby activate
(E) exhibit which, as a result, activates

In the correct option, "exhibit" and "activate" both are in a // structure. That implies, "visitors" did both the actions i.e., "Visitors activated animated functions" instead of the intended meaning that "touching an exhibit activated the animated functions.

This is the intended meaning: the visitors' act of "touching" the exhibit will activate its animated function. Let me explain with an example:
We invite the chief guest to light the lamp, and thereby inaugurate the function.

This means that the chief guest's act of lighting the lamp leads to the inauguration of the function. The chief guest or the lamp lighting are not treated in isolation. The same structure is followed in the right answer choice D, which we can arrive at through the process of elimination in any case.

(A) exhibit, which thereby activates - 'exhibit' doesn't activate, it is the 'touch' that activates
(B) exhibit, in turn an activation of - Not parallel
(C) exhibit, and it will activate - 'it' has no clear antecedent
(D) exhibit and thereby activate - Neat and parallel
(E) exhibit which, as a result, activates - Not parallel

Gughan nailed it, but just to tack on a quick explanation to answer the original question:

The word "thereby" prior to "activate" in the correct answer serves to clear up your doubt. It's there to show that the two actions "touch" and "activate" are directly and causally related. It's like saying:

"Visitors are encouraged to touch the exhibits and, by doing so, activate..."

Logically, it's still the visitors that activate the animated functions (when you turn the key in the lock, you're still the one unlocking the door even if you're doing it by virtue of a tool), so the subject isn't wrong at all. I'd agree that you should be skeptical as the two events aren't totally separate, but the word "thereby" links them and should eliminate any issue with clarity.