An argument is more persuasive if your examples come from sources that are ___ A. atleast twenty years old
B. biased towards your position
C. empirical
D. measured in two different units

C is the best option

Explanation:

em·pir·i·cal

/əmˈpirik(ə)l/

adjective

based on, concerned with, or verifiable by observation or experience rather than theory or pure logic.

"they provided considerable empirical evidence to support their argument"

faulty parallelism is a grammar construction where there is no balance in the parts of a sentence they have a similar meaning but the grammar structure is not equivalent.

the correct version of this faulty parallelism in the sentence is:

jefferson wrote the declaration of independence, and he was the nation's third president.

the problem with the first version is that the sentence:

"jefferson was both the writer of the declaration of independence"

presents jefferson as both a subject and an agent for the verb "write" because if he was "the writer" then the declaration of independence was written by him, besides that fact, the sentence presents a dependent clause.

while the second sentence:

he was the nation's third president.

presents a basic subject+verb+object structure

so, to give a proper balance to the structure, or better said, to give a parallel structure, we must write a basic s+v+o structure in both sentences:

jefferson wrote the declaration of independence, and he was the nation third president.