Sentences can be correctly punctuated in a variety of ways, depending on the emphasis that the author wants to give different pieces of information.
which of the following sentences has incorrect mid-sentence punctuation?

a) the main purpose of parkour is to keep moving forward by combining various movements—such as the roll, cat leap, precision jump, kong vault, and speed vault—in a fluid fashion.
b) the main purpose of parkour is to keep moving forward (by combining various movements such as the roll, cat leap, precision jump, kong vault, and speed vault) in a fluid fashion.
c) the main purpose of parkour is to keep moving forward by combining various movements (such as the roll, cat leap, precision jump, kong vault, and speed vault) in a fluid fashion.
d) the main purpose of parkour is to keep moving forward by combining various movements, (such as the roll, cat leap, precision jump, kong vault, and speed vault)—in a fluid fashion.