求教GWD 20-31

Q31:
                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.

1. exhibit, which thereby activates

2. exhibit, in turn an activation of
3. exhibit, and it will activate
4. exhibit and thereby activate

5. exhibit which, as a result, activates

答案为D，请问为何不选A？

万分感谢~

In GMAT SC, it is a deadly sin to use "which" to refer to the general meaning of a preceding sentence. This is true even we have been educated to use "which" this way. Put it another way, correctly used, "which" must have a referent that is either a noun or pronoun (or noun/pronoun phrase.)

It might help if you read the OG again to get familiar with this and similar rules. If you have never read OG, it is a good idea to start now.

想问thereby activate 是省略了to吗?