Ignore the first part.
Neanderthals fashioned finer implements, tapering from the butt to the point and flaked on two sides, to form the familiar teardrop now paradigmatic of early man.
A. point and flaked on two sides, to form
B. point, flaked on two sides, and formed
C. point, flaking on two sides, that form
D. point, flaking on two sides, forming
E. point and flaked on two sides, form
the middle part is a modifier, tapering from...., describing the "finer implements"
What is the quality of the implements? "
tapering from the butt to the point and
flaked on two sides"
One is "ing modifier" and the other one is "ed modifier" so (A) is correct.
(B) is incorrect because flaked is not a verb, it is a ed modifier here
(C) is incorrect because there is no "and", no parallelism
(D) even if you think flaking is correct, 3 "ing" without and "and" also fails at parallelism
(E) verb ... verb incorrect. Neanderthals fashioned ... form. You cannot have two verbs like this without a conjunction