Two lengths, \(a\) and \(b\), are measured to be \(51 \pm 1{\text{ cm}}\) and \(49 \pm 1{\text{ cm}}\) respectively. In which of the following quantities is the percentage uncertainty the largest?

A.     \(a + b\)

B.     \(a - b\)

C.     \(a \times b\)

D.     \(\frac{a}{b}\)

B