Which of the following monosaccharides are present as have membered
cyclic structure (furanose structure)?

1.  Ribose

2.  Glucose

3.  fructose

4.  Galactose

 
(a, c)
Ribose and fructose have five-membered cyclic furanose structure because it includes 5 carbon atom containing polyhydroxy carbonyl compound.
Hence (a) and (c) are the correct choice.