When determining the number of significant digits in a measurement,
a.
all zeros are significant.
b.
all nonzero digits are significant.
c.
all zeros between two nonzero digits are not significant.
d.
all nonzero digits are not significant.

b.

all nonzero digits are significant.

Explanation:

Significant digits are total number of digits that are used to define the final results.

So here we have to define as per rules

1) All non zero numbers are significant

2) All zeros between two non zero numbers are significant

3) All trailing zeros in a number without decimal are not significant

4) All zeros in a number which is greater than 1 with decimal are significant

So as per above rules correct answer will be

b.

all nonzero digits are significant.

b

explanation:

if the person is shown to have +90n, then ans is -10n.

if the person is shown to have -90n, then ans is +10n.