When examining a number with trailing zeroes and no decimal point, such as 2000, choose the best answer for determining the number of significant figures. A. Assume numbers such as this are exact and therefore have an infinite number of significant figures.
B. Numbers such as this are considered ambiguous, and we shouldn't write them. Instead, we should put numbers with trailing zeroes into scientific notation so that we clearly indicate the correct number of significant figures (exact numbers are exempt)
C. You simply count up all the digits and assume they are significant.
D. We just only count the non-zero digits, and assume zeroes are not significant.