[单选题]
How many water molecules aoh 69zolg.a 0 w16izzare there in 36 g of water? Express your answz*2-pgvm d1 fe v3*su dg.pv/rer as a multiple1-.p3vdpedv g/m**uf vr sgz2 of Avogadro'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
