Let us calculate the significant figures of each of the given measurements.
[tex]1.02 \times 10^{-3} g= 0.00102[/tex]
We know that the leading zeros are non significant.
Hence, the number of significant figures is 3
Similarly, 0.089 g has 2 significant figures.
100 has 1 significant figure because trailing zeros are non significant.
Finally, [tex]7.8 \times 10^{-6}= 0.0000078[/tex] has 2 significant figures.
Therefore, [tex]1.02 \times 10^{-3} g[/tex] has three significant figures.
A is the correct option.
