Two of them
4
It has two significant digits.
It has 3 significant digits.
3 significant digits.
Five. All nonzero digits are significant and zeros in between significant digits are significant.
All of the digits you've listed are significant. If we're supposed to perform some operation on them, the least number of significant figures in any number of the problem determines the number of significant figures in the answer.
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.
50.4 has 3 significant digits.
There are 4 significant digits in 5600.
This number has seven significant digits.