<p>I need explanations for these questions:</p>
<li>Now that Michiko finished the research, she feels reasonably confident about writing her paper on the rise of the progressive movement inthe United States.</li>
</ol>
<p>Right Answer: (A) finshed
Do I have to put past perfect?</p>
<li>Insomniacs have often established so firm a pattern of sleeplessness that the very act of lying down can make them more alert.
Right Answer: No error</li>
</ol>
<p>I put: (B) so firm</p>
<li>Chess players find that playing against a computer is helpful to improve their skills, even though no chessplaying computer has yet won a championship.</li>
</ol>
<p>I knew right answer was <(A) to improve>, but why is it wrong?</p>