Scientific writing

Which of these words does NOT describe how a scientific article should be written

Which of these words is a contraction

Which of these explanations is not a reason for an article being clear and concise.

What is a contraction

How old does an article need to be, to be considered no longer credible

Which of these is NOT a technique for an objective writing style

Which one of these techniques represents a objective writing style

Which of these words is considered to be 'Too informal'