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)."

abruptly

600 grams is the answer