We know in a triangle the sum of lengths of two sides is always greater than the length of the third side.
Now we have, \(3cm,4cm,5cm\)
So, \(4+3 \gt 5\)
\(7 \gt 5\)
For \(2cm,4cm,6cm\)
\(2 +4 \gt 6cm\)
\(6 \gt 6cm\) Which is not possible.
For \(2.5cm,3.5cm,4.5cm\)
\(2.5+3.5 \gt 4.5\)
\(6 \gt 4.5\)
For \(2.3cm,6.4cm,5.2cm\)
\(2.3+6.4 \gt 5.2\)
\(8.9 \gt 5.2\)
Hence Correct option is b