All four of them.
Four - zeros between significant digits are significant.
5 significant figures.
No, 3 of them.
1 fluid ounce = 29.57353 mL (to 7 significant digits)
Five, because if they were not significant, the final two 0s should not be there.
157.725 ml is the answer if 0.6667 is an exact measurement. If it's an actual measurement, you only have 4 significant digits of precision, and the answer is 157.7 milliliters.
Five. All nonzero digits are significant and zeros in between significant digits are significant.
Integers ending in 0 are ambiguous cases. The measurement could be accurate to the units digit and in that case all three digits are significant. But is could be accurate to the nearest ten, in which case, only the first two digits are significant.
Five. All nonzero digits are significant and zeros in between significant digits are always significant.
Five. All nonzero digits are significant and zeros in between significant digits are always significant.
Five. All nonzero digits are significant and zeros in between significant digits are always significant.
Four - zeros between significant digits are significant.