Answer
The correct number of significant figures for the 4 parts are listed below:
a) 2
b) 2
c) 3
d) 3
Work Step by Step
a) 24 is a whole number and all digits are significant so 2 is correct.
b) $5.6 \times10^{-12}$ has 2 significant figures as it's a decimal and there are no zeros as well so all digits are significant prior to the multiplication.
c) 3.14 is a decimal number and all digits are significant with no zeros so all digits are considered significant thus 3 is correct.
d) 0.00383 has only three significant figures because all of the zeros prior to the numbers are insignificant as there is no bar above the number to indicate significance.