Which sentence is punctuated incorrectly?
a. he explained the principle of internal-combustion (although not very well)
b. john lennon (1940-1980) was a founding member of the beatles.
c. the latin expression "per se" ("in itself") has found wide use in legal circles.
d. fredrick (not known as "tex") was becoming a well-known animator.

Option A. He explained the principle of internal-combustion (although not very well)

Explanation:

Option A is missing a period at the end of the sentence.

Periods are used at the end of any sentence that is intended to make a statement. The period should be placed directly behind the last letter of the last word of the sentence.

In this case, after finishing a sentence with parenthesis, a period should be set after the parenthesis, not after the last word inside it.

"... (although not very well)."

to gain popularity at school, fitzgerald wrote plays for the school and cast himself as the star. he also joined one of the universitys most prestigious clubs.

the answer is a)   a sentence of death costs the state "almost three times as much as a sentence of life in prison" (delon 147)