Choice displays appropriate use of parallel structure and correct use of commas?

a) to boat, to ski, and sunbathing are three activities in which a person can take part at the lake.
b) to boat, to ski, and to sunbathe, are three activities in which a person can take part at the lake.
c) to boat, skiing, and to sunbathe, are three activities in which a person can take part at the lake.
d) boating, waterskiing, and sunbathing are three activities in which a person can take part at the lake.

D) Boating, waterskiing, and sunbathing are three activities in which a person can take part at the lake.

Explanation: Parallelism or parallel structure is a literary device that consists in the repetition of the grammatical structure of words or phrases in a text. In the given sentences we can see a list of elements, in order to them to be correct, they must be consistent in the form of the nouns and verbs (they should be all in the infinitive form or all in the gerund form), so the options B and D use parallel structure correctly, but option B have a comma before the verb which is incorrect (we should not use commas to separate the subject from the verb), so the correct answer is option D.  

kennedy creates personal credibility by saying he is more than fit to lead. he talks about the sixty day period that he constructed administration, and says based on that he will be an acceptable leader.

jfk has a great reputation as an american citizen. he fought in wwii, and earned the navy and marine corps medal. he saved several men on his pt-109 patrol torpedo boat after an attack by the japanese navy. he also served in congress for the 11th congressional district for massachusetts, and served three terms in the house of representatives.

explanation:

mailman is the most possessive answee