Final answer:
Maintaining parallel structure, the correct completions are 'creative, persuasive, and effective' and 'comes to class on time, participates in class discussions, and submits his assignments before the deadlines.'
Step-by-step explanation:
For sentences to be parallel, the structure of the phrases must be consistent. Looking at the first sentence, the answer should be 'creative, persuasive, and effective.' All adjectives are in the same form which maintains parallel structure. The other options 'persuading' and 'effectively' break the parallelism because they are not adjectives like the first two words.
Regarding the second sentence about John, the correct series of phrases would be 'comes to class on time, participates in class discussions, and submits his assignments before the deadlines.' This maintains verb consistency in the present tense for all items in the series. The other options provide a mix of different forms (participial and gerund forms) that disrupt the parallel structure.