Trust is the root word. Dis is the prefix, and there is no suffix in Distrust.
Answer:
Test are useful in determining Charlie's suitability for the experiment.
Answer:
Study, study, study! I can’t really tell you what not to study, but focus most on subjects you aren’t the best at. Say your best subject is history. You don’t want to study hard on history when you already know all that. Study your weak points. Good luck, and I hope this answers your question!