SOLUTION
From the triangle inequality theorem, the sum of the lengths any two sides must be greater than the length of the third side
So, looking at the options and looking at 4 and 5, it means that 5 is the longest side. So
[tex]\begin{gathered} 4+2=6>5 \\ 4+4=8>5 \\ 4+1=5=5 \\ 4+3=8>5 \end{gathered}[/tex]
So since 4 + 1 = 5 and 5 is not greater than 5, hence 1 cannot be the length of the 3rd side.
The answer is option C
