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Explanation:
Use a marker to highlight the first three digits on the left. That would be the 7, 0 and 0.
The digit just to the right of that second "0" is the digit "9". Since this 9 is larger than 5, we'll bump the 7.00 up to 7.01
The 0 in 7.01 is significant because it's between two nonzero values. So we have three sig figs here.
