Question 831666
For isosceles, reject choices #3 and #4 immediately, since you must have two sides equal.  Examine choices #1 and #2 using the Triangle Inequality Theorem.  


#1:
1+1<3;
1+3>1.
Trying to connect 1 unit lengths on both endpoints of a segment of 3 unit length, and then moving the unconnected endpoints of the two 1 unit segments, will not connect.  


#2:
6+6>5;
5+6>6.
THIS ONE!!!