The question requires us to identify the amount of significant figures in the conversion 1000 mL = 1 L
To answer this question, we must keep in mind that trailing zeros are a sequence of 0 digits in a number after which no other digits follow. Considering that definition, we can say that the zeros in the number 1000 are trailing zeros.
Now, taking into consideration that trailing zeros will only be significant if the number has a decimal point, the number of significant figures in 1000 is 1 rather than 4.
Therefore, as the number 1 also presents only one significant zero, the best option to answer this question is 01.