To find out if the three side lengths can create a triangle, the three smaller lengths must be greater than the longer length.
\(\bf~Option~A\)
\(\sf~3~meters,5~meters,7~meters\)
\(\sf3+5=8>7\)
So this can create a triangle.
\(\bf~Option~B\)
\(\sf1~yard,1.25~yards,1.5~yards\)
\(\sf1+1.25=2.25>1.5\)
So this can create a triangle.
\(\bf~Option~C\)
\(\sf5~inches,10.5~inches,17~inches\)
\(\boxed{\sf5+10.5=15.5<17}\)
So this cannot create a triangle.
\(\bf~Option~D\)
\(\sf15~millimeters,18~millimeters,30~millimeters\)
\(\sf15+18=33>30\)
So this can create a triangle.
Therefore, your answer is Option C.
