It is the subject verb agreement.

Scripted boulders "..." INCLUDE

C also has include. No subject-verb issue there

C changes the meaning.

Original sentence tells Vir is an example.

C says other.

Scripted boulders found at Lepenski Vir, an example of the earliest monumental art known from central and western Europe, includes 15 figures with human features similar to Upper Paleothic forms and to Middle Eastern Nantufian stone figurines.
a)Vir, an example of the earliest monumental art known from central and western Europe, includes --- Includes is wrong (Subject Verb issue -- Subject here is scripted boulders which is plural so it should have plural verb i.e. include) moreover "an example" is also wrong here (an example refer to Scripted boulders which is Plural in nature)
b)Vir, examples of the earliest monumental art known from central and western Europe, include
c)Vir, earliest of monumental art known from central and western Europe, include
(It does not have the Sub-Verb agreement error but it changes the meaning of the original sentence by suggesting that the scripted boulders at XYZ are THE earliest monumental art rather than the examples of the same. )
d)Vir are examples of the earliest monumental art known from central and western Europe and includes
(It is wrong because of the usage of singular verb form which is includes since the first part before and uses the correct verb form)
e)Vir are examples of the earliest monumental art known from central and western Europe, including
(this option tends to change the meaning of the sentence the main verb from the original sentence becomes the modifier (Main verb ==> include ; modifier ==> example statement )and the modifier becomes the main verb )

Why not E?