<p>In a plane, two regions, S and T, are called “unlinked” if
(1) S has no points in common with T, and
(2) Any line segment that can be drawn with both endpoints in S<br>
has no points in common with any line segment that can be<br>
drawn with both endpoints in T.
Which of the following shows a pair of regions that are unlinked?</p>
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<p>I need the explanation plz, thanks</p>
<p>If you look at the requirements for S and T to be “unlinked,” item (1) means that S and T should not overlap at all. That rules out E. I’d interpret D to have T as the center circle, and S as an annulus, separated from T by a blank space. So A, B, C, and D all meet condition (1). Now go to condition (2). To make (2) false, you just need to find a line segment with its endpoints in S that contains a point in T. Then you can draw a line segment with its endpoints in T that contains that point, and condition (2) is not met. Look at the different pictures, and see how you might draw a line that has endpoints in S but runs through part of T. Rule out any diagrams that permit that. What are you left with?</p>
<p>^yeah, I got it now! THANKS! :)</p>
