<p>Why d?
I don't have a clue</p>
<p>whats the question?
post it next time</p>
<p>well in (a,b), the "a" must be less than four because the shaded region only reaches up to 4. </p>
<p>In some parts of the area "b" is greater than "a" so you know II is false.</p>
<p>And of course b has to be less than the y coordinate of when you plug in "a" into the function otherwise b would be outside the shaded area.</p>