Chapter 2, Problem 84UTC

The chapter sections to review are shown in parentheses at the end of each problem.
In which of the following pairs do both numbers contain the same number of significant figures? (2.2)
$\begin{array}{l}a.3.44\times {10}^{-3}gand0.0344g\\ b.0.0098sand9.8\times {10}^{4}s\\ c.6.8\times {10}^{3}mand68000m\\ d.258,000gand2.58\times {10}^{-2}g\end{array}$