Which of the following measurements is the most accurate?

The number of significant figures in $4.870 \ m$ is

Statement-$1$: All reliable digits plus the first uncertain digit together are called significant figures.
Statement-$2$: Trailing zero$(s)$ in a number with a decimal point are never significant.

What is the number of significant digits for a number that does not represent a measurement?

Write the rules for rounding off numbers.

State the number of significant figures in the following:
$(a)$ $0.007 \;m^{2}$
$(b)$ $2.64 \times 10^{24} \;kg$
$(c)$ $0.2370 \;g \;cm^{-3}$
$(d)$ $6.320 \;J$
$(e)$ $6.032 \;N \;m^{-2}$
$(f)$ $0.0006032 \;m^{2}$