How many significant figures are present in the following?
$(i)$ $0.0025$
$(ii)$ $208$
$(iii)$ $5005$
$(iv)$ $126.000$
$(v)$ $500.0$
$(vi)$ $2.0034$

$(i)$ $0.0025$: Leading zeros are not significant. Significant figures = $2$.
$(ii)$ $208$: Zeros between non-zero digits are significant. Significant figures = $3$.
$(iii)$ $5005$: Zeros between non-zero digits are significant. Significant figures = $4$.
$(iv)$ $126.000$: Trailing zeros in a decimal number are significant. Significant figures = $6$.
$(v)$ $500.0$: Trailing zeros in a decimal number are significant. Significant figures = $4$.
$(vi)$ $2.0034$: Zeros between non-zero digits are significant. Significant figures = $5$.