Step 1: Recall the formula for the diagonal of a rectangle.
The diagonal $d$ of a rectangle is given by:
\[
d = \sqrt{l^2 + b^2}
\]
where $l$ = length and $b$ = breadth. Step 2: Substitute the given values.
\[
d = \sqrt{35^2 + 12^2}
\]
\[
d = \sqrt{1225 + 144}
\]
\[
d = \sqrt{1369}
\]
\[
d = 37 \, \text{cm}
\] Step 3: Conclusion.
Hence, the length of the diagonal is 37 cm. Correct Answer: 37 cm