I think it is E.

A, B, and C have the discovery as subject. This means that the discovery itself provides mixture. This is wrong because the Oak tree sap should be subject, not a modifier.

D is wrong because the placement of "can" looks awkward. Moreover "and at lower cost" is just a fragment.

E is correct because subject is oak tree sap. Moreover the placement of and is parallel...i.e, "Will be able to provide.........and to decrease the cost"
_________________

"Not everyone who works hard succeeds. But all those who succeeded have worked hard!" ~~ Coach Kamogawa

Best,
ItsNotOver

IMO B. "The recent discovery" is anticipated to advance the experimentation not "The Red Oak Tree Sap"

I go with D as well.. Concise and correct meaning.

IMO:D. A recently.....will be.....,and at a lower cost I think is grammatically correct.The subject of the sentence is red oak tree sap,the discovery of which will provide the provide chemists with a more potent mixture.I think the OA will read as D!

The recent discovery of a red oak tree sap that is anticipated to advance experimentation with natural substances in order to create cancer medicines will be able to provide chemists with a more potent mixture to work from than other trees and at a lower cost.
(A) The recent discovery of a red oak tree sap that is anticipated to advance experimentation with natural substances in order to create cancer medicines will be able to provide chemists with a more potent mixture to work from than other trees and at a lower cost

Doesn't compare sap of one tree with the other.

(B) The recent discovery of a red oak tree sap is anticipated to advance experimentation with natural substances in order to create cancer medicines and will be able to provide chemists with a more potent mixture to work from at a lower cost than the sap extracted from other trees

Best choice.

(C) The recent discovery of a red oak tree sap, which is anticipated to advance experimentation with natural substances in order to create cancer medicines, will be able to provide chemists with a more potent mixture to work from at a lower cost than other trees

Incorrectly compares mixture with the trees.

(D) A recently discovered red oak tree sap, which is anticipated to advance experimentation with natural substances in order to create cancer medicines, will be able to provide chemists with a more potent mixture to work from than the sap extracted from other trees can, and at a lower cost

A comma before a conjunction indicates that there has be a clause following conjunction, and a clause should have a subject and verb. In this case, it's just a prepositional phrase with an object, so this choice can never be true.

(E) A recently discovered red oak tree sap, which is anticipated to advance experimentation with natural substances in order to create cancer medicines, will be able to provide a more potent mixture to work from than other trees and to decrease the cost

Incorrectly compares mixture with trees, and "to decrease the cost" has problem of ||ism.
_________________

If I look absent-minded or insane, I am just living a dream of being successful. If you still wonder why I am like this, you have no idea how success tastes like!

This is a good question. thanks for posting.
_________________

"Not everyone who works hard succeeds. But all those who succeeded have worked hard!" ~~ Coach Kamogawa

Best,
ItsNotOver

i am totally lost in it. surely i'll be broken down if i see this kinda SC on G-day
_________________

some people are successful, because they have been fortunate enough and some people earn success, because they have been determined.....

please press kudos if you like my post.... i am begging for kudos...lol