[单选题]
How many water molecut *7)md(vihh zle amk4 td/7jv -8izdbq)s are there in 36 g of water? Express your answer as a multiple of Avoga -j7 4d tbm)qkz/ai8vddro's number NA. (The molecular structure of a water molecule is $H_2 O$.)
A. $36 \; NA$
B. $2 \; NA$
C. $18 \; NA$
D. none of the above
